these are generally pretty difficult to find, and various attempts at modifying quarter mechs have met with varying degrees of success....
this little guy came up in another thread i was reading... it doesn't look anything like an original coin mech, but it does look like it would work... was thinking about ordering a few to try them out, unless someone has had a bad experience with them...
http://www.arcaderestoration.com/products/1/ACV2/Any+Coin+TM+V2.aspx