I'm a fan of the Kamoer dosing pumps. Mine have been running for 7-8 years without issue. And the price is competitive. I have the X1 but I think they're on newer models now.
If you're going to be dosing alkalinity and calcium, you may want to take a look at your magnesium too. If it gets too low you get a "see-saw" effect between alkalinity and calcium, where when you dose one the other drops. Magnesium helps prevent that. Once I started dosing a lot of calcium and alkalinity with my dosing pumps, and my coral growth exploded, my magnesium started to drop and I had to get a dosing pump for it too.