i had to find a picture of one, and although the wheel might be difficult to true, it's not impossible. if your wheel isn't bent to begin with, it should true right up. your bike store is either lazy, incompetent, or both. it might not fit on their true-ing stand, but it'd be simple enough to do on the bike.
as far as spokes go, to get 12g. (.105) spokes, you'd need to measure the length of one of the original ones. to do this, you measure from the top at the inside of the bend to the end.
if you tell me how long, i could help you find some.
the fun part, is you'll probably have to re-drill your rim and hub. sometimes you get lucky and they fit, but usually not. if it's an aluminum hub it's a piece of cake. if it's steel, it's a pain, and you better buy extra drill bits. also, you have to have enough "meat" on the hub so it won't compromise the strength.
drilling rims and hubs is common practice, and i've done it myself with no problems, so it's no big deal.
the real problem is finding someone to do it, if you don't think you can handle it.
but if you're breaking spokes, bigger is the way to go.
if you want to spend some real money, you could probably find a motorcycle shop that could rebuild it with 10, 9, or even 8 gauge spokes. then it'd be like a motorcycle wheel. it'd be overkill, but it'd be mighty cool.