Here is another thing. Duct or clear, wide packaging tape and a tube of GOOP brand glue are your drill and drill bit. Say you have room or an open gap where you if you looked inside the front fairing, there is someplace you could wedge that pump into place. Say the way to do it is to drill through the fairing to mount it up.
See, all you need to do now is to find the 'touch points' to the pump to that spot on the fairing, side cover, or winker cavity; are 3 areas I can think of right off the bat. You have a lot of options because you think, 'I need to drill to mount' is your only option. Forget about under the seat as you can see.
I found my touch points to the throttle actuator, glued them in place. She has seen 140-plus so far on her surface and she is still hanging out in the wind waiting for more. That is how strong that glue application can be.
Go to a home center type chain store, then look for that brand name. Or google "GOOP glue" with capital letters. Then watch the flash build a ball and chain kind of glue my bowling ball to my TV together kind of strength. Once you find your mounting hole, glue your touch points, run a strip of tape over the pump or the pump will slide. You'll see what I mean as how to work with the glue. It takes more than 24hrs for the glue to setup before you can push or pull your air tubes off without the unit moving. You could pull the tape off within hours of setting up. But, I find 48hrs is cured better, where you can apply more pressure on the unit from moving any. The best part about this glue is you can peel it off. Looks like it was never on the bike, fairing or paint.
Just throwing out an option no matter the size of that pump >> Glue it in place.
Tormenting the motorcycling community one post at a time