I think there's a large enough market for repro covers, that and the front smoked piece covering the controller ports are by far and away the most broken and missing pieces I've seen on the 5200. I've got a 2-port 5200 with a chunk taken out of the front piece and I'd love to get a new replacement.
Same here - I had a pristine system and dropped it one day and broke both of those panels. Been looking for a donor system ever since. It's surprisingly hard to find one that fits the bill. Either systems are pristine (like mine was), come with a box, all accessories and a bunch of games and cost $200+, or they're total junk, at minimum have these panels scratched up, but usually broken or missing too. I haven't found a 2 port unit by itself in really good condition for a half decent price yet.
Maybe I'm too exacting; these panels on my system still don't have a single scratch on them. They're both cracked/broken, but no scratches... so it's hard for me to replace them with panels that are all scratched up. At the same time, I don't want to pay $250 for two plastic panels. (I know I could sell the system later, but wouldn't get near that price if I swapped the panels out, and 5200's are a bitch to ship!)