I suppose one could make an adapter of sorts to fit the wiper motor right to the lead screw. I looked the lead screw area over quickly last night, I'm not sure there is enough room to put a bearing of sorts in there. Naturally a new lead screw support would need made up, but I'm not sure you would find bearings small enough to make it work.
I tend to agree with "uncle harry" above. A timing belt and toothed pulleys shouldn't put that much more tension on it.
My mill uses a timing type belt to run the head with toothed gears, its been running that way for over 30 years, never a problem.
Thanks to all for some excellent suggestions and advice.