I have an old Schwinn Varsity 10spd(June 1970) that I got for free, replaced cables, tires, innertubes, bar wraps, etc. Here is the problem though. The spring in the old Schwinn Approved rear derailleur is too weak to keep enough pressure on the chain. I can ride it fine in the second highest gear but when I shift the rear to go into 10th it will still ride but the chain slips. I figured it would be easier to just buy a cheap vintage derailleur to replace it with.

I know it has to be for a 5spd cassette and I think it has to be long cage? I might consider getting indexed bar end or thumb shifters (of which I will need proper cabling, right now just using crappy Bell cables from walmart). Also, it has to look crappy. I know its a weird request but its a college town and I have seen many bikes that have been stripped of parts while still chained up... So something inexpensive, that will actually shift, and is preferably old or cheasy looking. Any suggestions?