Glock 43x. You keep the same sight picture, trigger feel as your 19. I think the grip is the same length too. The width and barrel are smaller/shorter thatn your 19. You can get shield mag that gives you 15 rounds. You will need to change the mag release. You can go to Palmetto State Armory, and look up their Micro Dagger mags. They are 15 rounds, but you can keep your same mag release. They are hard to keep in stock, so you may spend a lot of time looking for them.