I wouldn't limp one tenth of a mile, let alone 8, unless you have a deep desire to find out how to replace bearings and seals in your transmission. As for finding a used one, many prop shops have numerous old props lying around their shops. Any of the propeller manufacturers can supply you with a new prop, but it might be nice to figure out why the blade fell off. If it had to do with electrolysis, then you should fix that before putting a new prop on.
This might be a very good time to change to a feathering prop, which should greatly improve your boat's performance under sail. I really liked my MaxProp.
Sail your boat the 8 miles, anchor outside the marina, then get a tow to your dock.