Retaining Ring Removal

[darrel_s]

Looking for some technical advise. While cleaning up my NP205 transfer case, some sand got into the bearing where the adapter fits up to the transmission. I was able to remove the outer ring with ease, but the inner ring is way to strong and doesn't have enough lip to open with the same flat head screwdriver technique. Hopefully the pick will illustrate the location of the problem a little better.

Since the 10 cent method isn't working, is there a special tool I can buy to open this ring up? If so where can I get it? Thanks in advance