Early reports on the LCR called the gun J frame sized and asserted it would fit J frame holsters. Your thinking that a J frame holster would fit may be based on remembering those early, and incorrect, reports.
The Simply Rugged Silver Dollar Pancake can't be beat. I have one for my 3 inch SP101's and will be ordering one for my LCR as well.
The LCR will fit a Desantis Nemesis pocket holster for J frames. I must report I find the LCR to be a tad to large for pocket carry, for me, as it just doesn't draw as smoothly from a pocket as a Centennial. IMO, the Nemesis is the best pocket holster going if you should decide to give pocket carry a try.
YMMV