The tolerances of this mini water pump are very tight, so it may take a few adjustments to get it to work properly. I recommend ceiling the joint between the top half and the bottom half with hot glue, epoxies or some sort of waterproof glue.

You only need 4 of the self tapping screws Linked below.

What motor?

Any motor that is 15 x 19.9 mm should work.

Motor number,  29DCM1