I see them on ebay from time to time. Make sure you get one that has the horn button in the middle. I have made the mistake of getting a steering wheel off of a 1979-up Mustang/Fairmount only to realize that the turn signal stalk...when pushed "in"......is the horn button. No provison for a horn button on those steering wheels.
if you have some pintos in junkyards look in them as well. i found a few in pinto wagons.. also granada ess's have a nicer leather wraped wheel. there hard to find but there out there.. if you find a granada ess please let me know..
I'd go custom with the steering wheel. Mainly because you can be looking forever before you find one that in decent shape or one you like.
I already have a Grant Steering wheel, which looks very nice, I just like the style and factory musclecar look of the Mustang-II type. So at least I have something decent on the car while I'm searching...