Do you have a home depot near you?
You can probably make one in about 20 minutes:
1. Flat metal bar the same width as the 'retaining ring'
2. Dremel tool with cutting bit
3. Remove a large gap of metal inbetween both sides of the metal bar; leave the edges long to fit the slots on the 'retaining ring'.
Done
You could also try needle nose pliers, but you could slip and scratch something.
Good luck