This adapter allows you to install a pump on a large hand soap bottle that does not come with one and is typically used to refill smaller bottles.  Save a pump from an old soap or lotion bottle and install it on a refill soap bottle.  The adapter seems to fit most of the refill bottles and pumps that I have run across so far.  There is an adapter gasket included that you can print with TPU and use if you want to, but it is not necessary.

The straw will probably be too short to reach the bottom of the bottle, so print and install a straw extender.  There are a few included, but you might have to design your own because there are so many different straw diameters and lengths out there.  You can make the extender just long enough to reach the bottom straight down, or you can make it longer and push it off into one corner to pump out even more of the soap.  In this case, you may need to use PETG and / or a thicker wall due to the bending load that will be imparted into the straw extender.

Also, you can add straw extenders to existing soap, shampoo, and lotion bottle straws to pump out more of the product before the pump starts sucking air.  I have found them to be quite useful.