Out of curiosity, I did a search myself....

I guess ALL vintage Mopars are now show poodles? Didn't matter if it was a truck or a car, I can find headlight switches no problem, but, ZERO wiper switches.



I'd be willing to bet it would interchange with a '70's A-body switch. Later ones had electric windshield washer built in.

Aside from that, and going used, maybe a generic switch? Its a pretty basic switch, here's one I found:

Wiper Switch

As an aside, I had an '84 that needed its heater control panel replaced (fan switch overheated and took it out). Came to find out, it was identical to one I had in my parts stash from a '77 FURY (B-body). No mods at all to install it.
Chrysler wasn't known to reinvent the wheel every year when it came to stuff like this, so, chances are good you can find something off an earlier car/truck that will work.