plastic bottle pumps that work upside down

I’m looking for a pump that will dispense the contents of what is basically an upside-down foil pack with a standard threaded closure. Something similar to that of hand soap dispensers, but screw-on. Any ideas or places to look?

try a search for PERSITALTIC PUMPS… they’re food grade if that is important.

Otherwise, the soap dispensor pump is called a Reciprocating Piston Pump
but it uses a ball and a spring instead of a piston… but i may be off… a while since i touched on that subject.