The LC9 comes with a finger grip extension. Did the one you handled have this installed? With the extension, it's still pretty short overall and like you, I can barely get third finger on grip.
I wanted a spare magazine and ordered this from Midway:
https://www.midwayusa.com/product/83...th-finger-rest
It made the gun fit much me more comfortably. However, it's extremely difficult loading 8, much less 9 rounds.
I'm not pushing this pistol for you. Just wanted to point out a way to make it fit better.
Good luck with your decision.