I think I'm looking at a hot water base board radiator, is that right? And you want to replace the covers? If so, they aren't all $100 per 4 ft, you can get them for 1/2 or 1/4 as much depending on size and style:
https://www.homedepot.com/p/NeatHeat...EAT4/203537675
https://www.supplyhouse.com/Slant-Fi...BoCh94QAvD_BwE
https://www.supplyhouse.com/Slant-Fi...RoCntgQAvD_BwE
They might be cheaper at local plumbing supply companies as well and/or if you buy them in bulk.

But to answer your direct question: I did make some panels for a cabinet around a large radiator, there are here http://www.talkshopbot.com/forum/sho...adiator-Grille

But that would take soooooooooooooooooooooooooooooooooooooooooooooo much sanding and painting for hundreds of feet that that it would be faster to refurbish what you have. I wouldn't strip them, I would clean them, sand the really bad parts and repaint them. I used white high temperature spray paint from Home Depot on some pipes and a radiator and it looks nice. Not perfect, but no one but me would notice.