It may not be necessary to pressurize it if you can produce it as fast or faster than the engine will consume it.
Most small engine carburetors can be modified to work as simple vapor units with only a few minor modifications.
The main jet, idle jet, and related mixture screw assembly's need to drilled out considerably over sized and the entire float system is removed as well.
What you are doing is just making the original fuel flow path much larger so that the less dense vapor fuel can easily be drawn through by the normal venturi effect that those small carburetors use to move the liquid fuels through them.
When done properly the carburetor will produce a very slight vacuum on the supply line so all that needs to be connected to is a container or supply source that can produce enough of what ever type of fuel you are producing. Ideally that source should also have a simple flash back arrestor of some type between it and the carburetor.
Most of these modifications require nothing more than a drill and some small drill bits. The rest is just trial and error sizing and adjusting to fine tune the set up.