There are several aftermarket outfits that sell the complete lever assembly....BugPac (Bug-Pac?) comes to mind...They're generally cheaply made and of low quality. I have one that came in my Spyder. It does work but I can't get my hand between the seats to activate it, so I might as well not have it...Absent any responses more intelligent than mine, I'd check with some of the dunebuggy and VW sites...By the way, the piece was basically the same for Beetles from '53 to something like '77 I think.
Also, someone on this site was in the process of designing and building a repro of the original 550 Spyder e-brake handle...Don't know where he is in that process.