A new magazine catch I designed to fix the broken one on my airsoft P90. May work for real steel ones, not tested.
UPDATE 8th Dec 2013: Added new files, original one was too tall to fit in the body of the P90 itself. New file also has wider grips.
Made with Sketchup and Netfabb to repair the inevitable holes caused by Sketchup.
Print with support. I printed without support on the initial test, it came out OK, but the small nub on the angled part was slightly deformed.
2mm support distance is sufficient to fix this.