Just had these serviced for the first time since buying them in the mid 70’s.
I’d now like to update them with original metal grills and the stands/legs that attach in the back.
Pretty low likelihood of finding the grills (unless you head to Germany). Here’s a thread where someone made a set for 810s but could be done for the 1020. The hard foam on the original grills gets pretty brittle so the use of plywood is a nice idea.
Your best bet is to check ebay.de regularly with "Braun LV 1020 Lautsprecher" as your search, but unfortunately most grills and stands will come attached to speakers, and won't be cheap.