It seems that the only time we talk about the coil is to tell our members to test it by putting a plug in the coil wire and hold it against a good ground on the head ,check for a good bright blue or weak yellow spark. How blue is blue? how yellow is yellow? If we use a volt/ohm meter the Clymer manual tells us to remove the coil and set the meter on the ohm's scales ,the primary resistance can be taken across the +and -  connections and should be between 1-7ohms,set a lead on either the + or - and the end of the sparkplug wire ,the resistance of the secondary should be 10k-25k ohms. This would give us a better idea of the health of the coil.      The coil is built very tuff and gives remarkable service.Charge time ,the time it takes to fully build a charge in the primary in our coil can be between 2.1-6 milliseconds,that voltage is between 12.5-14.5 normally ,(we know if voltage drops below 10 v while the starter is engaged we don't have spark at the plug) The field will then collapse ,inducing a current in the secondary,the voltage grows until it can ionize a path between the electrodes of the sparkplug ,allowing the plug to fire.      At an idle speed of 1000RPM the plug fires 16.66 times/per second, at a speed of 4140 rpm (about 65mph) it fires at a rate of 69 times/per second(248,430 /per hr.)       After market /racing  coils should never be used on our bikes ,these are high output and the voltage that can't be used by the plug can cause Flyback,which disturbs coil harmonics and can damage the TDI,they are also low resistance admitting EMI(electromagnetic interference) and RFI (radio frequency interference) which can also damage the TDI. These coils have charge times from .3-.5 milliseconds and are used with CDI 's, which send voltages of 30 to 500v to the primary coil but are only needed for motors that redline at about 10,00 RPM and above.

JOG the spark is driven off the crank so I think I did

OK.

Let's say I am traveling and my coil goes bust.

No OEM coil available.

What other possible coil ?

Will any coil do ?  

Coil, ignition box, what else?
There's the thing in the engine, name escapes me, thanks to the sixties...no, not the 1960s,

Stator?
Yeah, not a carry item, but I can see hauling bulbs and a coil. I've never had a coil go bad on a bike, but considering how hard it would be to get The Right coil from, even If it puked in a town, odds of someone having it on the shelf are slim.
So, in preparation for the trip, what besides bulbs and a coil should I have? It'd be Nice to have black box, but they are a rarely dead and always expensive item, aren't they?
Ya know, there's a motorcycle junkyard about forty miles from me. I should check it out.
I have an 02, I guess any year model coil would work, but if I could get the iggy module and decomp controller for cheap, I'd like that. Might as well grab a rectifier.  
Does anyone know what year donor bikes would work with the 02?

Unless you're going on the alaskan hwy, bulbs and fuses are common items.
and most of those pesky electrical items can be bypassed.  safeties, decomp controller, kickstand relay (WTF does that do anyway?)

Key items that would cause great concern for replacement, TDI, coil, stator, starter relay, and rectumfryer.

The TDI for us comes in 2 varieties, pre and post '88 (gonna have to check transition year) Other than timing (location of the sensor trigger) advance curves are more or less the same and done electronically per rpm.  I would think any single TDI and matching coil would serve as a replacement.  Of course there could be an issue with timing, so having a commensurate year may work.  As to whether you could replace 1 coil with another, probably.  Find 1 with the same size, resistance it may work.  Please remember that our coil will burn out the TDI if left on over night.  So I'd check the amperage of the coil as well.  These values may have to be checked by others so that we have values to check against.  Checking a burnt out coil ain't gonna work.

stator/rectumfryer, we already know a few models have a similar stator, although the wiring will be different, you should be able to splice it in.  and same for the rectumfryer.

Starter relay, worst case place the starter somewhere where you can get at it and jump the 2 terminals with a screwdriver.  Otherwise, any relay rated for the amperage will do, and others will work once or twice  

Versy , If I were planning a trip to Alaska, I'd be changing all the items first ,working on the bike on a dirt section of the al-can highway with a grisly bear looking over my shoulder as little appeal for me.I think my  spares would be more like ,tires ,tubes ,drive belt,and fuel.

Shotgun ,rifled,18.inch barrel,butt shorten to have a total length of 29 inches, meets federal law in all 50 states,12 gauge Remington copper plus ammo . a discouraging word that will be heard,even if the skies are cloudy all day!