Not sure what I can add here. Pipette bulbs, usually 2 mlj , used to work fine. The shorter you tie it the rounder it will blow up, but the less fuel it can hold. It's easy to tell when you've overfilled it. It bursts.
Pacifiers are better on older engines. They have much lower pressure which makes the needle valve easier to set. Pacifiers were around 6 psi. 1/4 x 1/16 wall bladder tubing is around 20 psi. 1/32 wall is in between but doesn't last very long.