Helm Starter switch twisting, help

[BugleCoveTinBoat]

I'm getting to the point I'll be mounting my helm on my 1967 Meyers 14' Laker Pro.
It's always been an odd boat, bow to stern seat (so the helm looks unusual).
Dad sold the original outboard and key switch back in the 70's. (Yes, I've had it a very long time.)
I'm looking for a way to secure my new starter switch. The inside of the helm is supported with plywood. My switch has a shaft that is .785 diameter with 2 flats at .725 Originally I believe it was set up for a 13/16 shaft with one flat.
I've been looking for an anti twist washer but I'm not finding anything that will work.
I'm thinking I should pull the plywood out and epoxy some flats to the inside of the hole.
Does anyone know of an easier fix?

 

[BugleCoveTinBoat]

I'm getting to the point I'll be mounting my helm on my 1967 Meyers 14' Laker Pro.
It's always been an odd boat, bow to stern seat (so the helm looks unusual).
Dad sold the original outboard and key switch back in the 70's. (Yes, I've had it a very long time.)
I'm looking for a way to secure my new starter switch. The inside of the helm is supported with plywood. My switch has a shaft that is .785 diameter with 2 flats at .725 Originally I believe it was set up for a 13/16 shaft with one flat.
I've been looking for an anti twist washer but I'm not finding anything that will work.
I'm thinking I should pull the plywood out and epoxy some flats to the inside of the hole.
Does anyone know of an easier fix?View attachment 124444