got an 2010 s40. looking for a larger gas tank to fit. any ideas??

Some folks need a bigger tank, some just want one,, Id suggest ya run a few thousand miles before you decide, unless you can SEE that youree runnin thru more gas than you can really deal with all the "Time to stop for gas" times. You runnin it down the road a lot?
How is it set up? Stock exhaust and jets? Have ya checked the MPG? Is it giving you a lot of poppin and banging? How many miles on it?
Theres a real recent thread on this.. Theres a tank that looks really "At Home" on it,, I think it requires a seat mod to get in up there, not sure,,
But,, the seat is an often maligned plank of foam rubber, so, a mod there is not a bad thing. YOU planning on riding 2 up or will you be solo?
Paladin had a seat that looked very comfortable. Kinda big, but, the headlight gave it visual perspective that made it look right on the bike.

headlight off a steam locomotive makes a seat off a tractor look sized reasonably,,

Would love to see some pics!