what's up doc??? sorry, couldn't help myself.
Acerbis make a tank for your bike (fit's 91 - 94 i think). Price all depends on your location and currency, obviously, but here in Australia I was quoted around $600 or $700 plus a 3 month wait to get one for my '94.
Clarke (think that's how it's spelt) also make a tank, but I think they might be an Aus company, which is prolly why they're a bit on the cheaper side for me.
Best & cheapest option is prolly just to scope out ebay untill one pops up. they'll go between $50 - $200 generally.
good luck with the hunt!