Sure, you can find USGI guns out there. However, [don't you hate that word?] be prepared to spend more then you think on a good one. They have had quite a run up in the prices in the past 5 years. While I have more then a few, I don't shoot most of them anymore because most of mine are original and getting into the thousand + of dollars as far as worth. I do have one that is a typical USGI mixmaster, Rem Rand slide and US&S receiver. Great shape and a decent shooter but not original.
A GOOD USGI will run you over $700 and go up from there anymore. You can find mixmasters for a bit less but they seem to sell at crazy prices also anymore. Thats whats happens when there is demand and a limited supply. You never know tho, you can sometimes get a steal on them. Be aware tho that many of the barrels are not in the best of shape due to the corrosive ammo used. They are safe but many are worn out. Collectability wise tho, the worn original barrel is better to have then a good replacement.
BTW, it's not really advisable to rebuild/refinish even a worn USGI 1911. It will kill it's value and ends up being just another frankingun worth $300. If you find one already wacked, go for it if you can get it cheap. Most people tho, think that it should be priced about 3X what it is really worth.