Make it yourself! (it's easy)
Just order on-line (ebay?) a used fuel gauge from a
kymco or bajaj motorcycle (from india, korea or china,
whatever as long as the case is shinny) or find one
at a motorcycle junk yard, then get a cheapy battery
powered pocket watch, open the gauge, carefully,
make some room for the watch.
Attach from under, somehow, I drilled a notch and used
a metal bracket and an aggressive metal screw, done.
ebay
http://motors.shop.ebay.com/items/__fuel-gauge?_arm=1&_armi=Motorcycles&_armm... They also sell these type of watches for your bike, an a different
model (like a large ring) that attaches to your handlebars , but
I like making my own.
Good Luck!