I bought my Rupp Roadster 2 roller on Craigslist for $100 and it has both wheels on it and the brake levers and both front and rear brakes work. It is missing the rear fender and I bought a used gas tank on Ebay. Ebay Rupp's tend to be expensive especially for the fully restored ones people ask $1400 to $1500 or more. I seen gas tanks on Ebay for more then I paid for the Rupp Roadster Roller. I will put a souped up Predator 212cc on mine rather than a Tecumseh HS40. The Predator 212cc with just a tiny bit of modification will make huge power and make the bike more satisfying and reliable for a 190 lb adult to ride than just a gutless old 4hp flathead Tecumseh. I may look for a Tecumseh HS40 for a good deal and swap out just to sell it for Top dollar since putting on a clone engine kills resale value on a Rupp.
All you need is a nice thick dense rebonded Foam seat and some people here on the forum make them.