USCamera custom light seal kit fits the Leica R4 and R4s.  This kit may fit other Leica R series film cameras, however, at this time I was only able to check for proper fit with the R4/R4s I have. I doubt it will accurately fit the R3 since it was a joint venture with Minolta using the XE body casting as a start.

This premium 11 piece kit includes 2 long channel seals on the body, 1 short channel seal on the body hinge end to counter lever, 2 channel seals on back cover (hinge end), 1 door hinge seal on back cover, short upper/lower back cover channel seals latch end, left/right mirror cushions and the film reminder window foam.

USCamera light seal placement guide for this Leica film camera here