Did you check the Marlow-Mainship section of the forum. There is a “Sticky” with some Mainship parts information. Don’t know if what you need is there or not. Maybe check with Bacchus, he seems to know quite a bit about Mainship stuff.
Bacchus here checking in
It doesn't look like anything on a 34 T/HT so the best I can offer is to go to the MS Parts links and scan through the thumbnail pics. If you find anything that looks similar cluck on the thumbnail and open the puc to confirm and see more part / source info.
Only other option would be to replace the whole fixture.