Let see if I understand. You need to replace the plate at the top with that pulley shown in place, and the gaping hole in front of it where the other pulley pulled off. Correct?
How hard is it to feed the wiring ( I think it's wiring) shown by my yellow arrow? Can you easily disconnect it, have a hole in the plate and pull it through it and reconnect? Is so you can just drill a hole for that. Be sure to bevel the edges. If not you may wish to cut a slot (bevel edges on that too).
The pulleys themselves and their brackets look like stainless steel and appear to be in decent shape. If you can't find a replacement part (preferred method), might be easy enough to take out the existing plate, use it as a template to build another plate out of stainless. The pulleys come off the current brackets by removing the cotter pin and take out the pivot pin. Then you could drill two counter sunk holes in the pulley bracket and the pbase plate and attach pulley to new base plate.
You could drill and tap the new stainless plate, put a counter sink on the top side of the plate, then when you put the screws to hold the brackets in, you can peen them over making sure they never come out. You could also rivet the brackets but I'm not sure where you'd get 316 stainless rivets... You can get 304 flush mount rivets from McMaster-Carr:
https://www.mcmaster.com/#rivets/=1967gvl
those could work. Might be cheaper to simply rivet if you have to buy taps....
Just some thoughts...
dj