I have a 1918 Singer Redeye treadle that belonged to my Great Grandmother. I have made one pair of boxers on it and that was enough for me.
I begged my grandmother for years to let me have it but it's really not as easy to use as i thought it would be.
Replacing the belt is easy. they are pretty cheap, 5-10 dollars, leather, just thread it through, figure out how long it needs to be to be SNUG, trim it, punch two holes and put a staple through. hopefully you have the staple from the original. If not you can really just use any old piece of wire. right now my staple is MIA (after moving) so I have a wire thingie from a dangly earring in there and it works fine.
If you want to go the true antique treadle route, pick up a real antique at an antique or junk store or garage sale etc. Do not buy one of the modern Singer treadles being made in China, they are terrible.
Also I would suggest you stay away from a pre-1920 (I think) Redeye machine as they have funky means of attaching the feet, so unless your machine comes with all feet, you will be hard pressed to find accessories, if this matters to you. I have such a treadle and one of these days I will get around to replacing the shaft to take standard side mount feet.
If you want to go fancy, check out www.lehmans.com
and they have modern treadles - not the Singers but a real modern machine that does zig zag and everything, made treadle for the Amish. Pretty cool!!!http://www.lehmans.com/shopping/prod...sewing+machine