Hello Mike,
Sad to hear that.
Yes, the combination swich on the steering column can be rebuild to some extend. One of our colleagues here did that - about half a year ago or so. I forgot who he was, he always signs with "64 230 SL fully sorted out - oops talked too soon" or so.
In general it is tricky to repair them, you need good hands for it.
You can also dismantle the black plastic handle itself, which is especially tricky. There is a little bolt/rivet on the handle, which holds the handle together and which is closed by a drop of glue and barely visible. I removed it with a little needle, it was a hard way but possible. When the handle breaks, there is hardly a possibility to repair it.
But maybe it's not the handle per se but the wiring somewhere. Even possible that the wiper relais does not work correctly. It's located on the left inner fender at a bracket in the engine bay.
For most of us, a new or a good used combination switch is often the only choice. They're expensive; DaimlerChrysler charges more than 400.00 Euros for the 001 545 55 24.
I try to find out this "repair" article, it might help although he didn't repair the wiper electrics but the turnsignal mechanism, which wears out mostly.
All the best,
Achim
(Magdeburg, Germany)