Hmm I spotted those on e(vil)Bay too and thinking of getting one. More important is the choice of compressor...a lot of those 'handy' 12v ones out there are built to do the volume of a car tyre, not the volume of a SUP, so I'd be wary of buying too cheap & light-duty only to have it burn out halfway through your SUP.
You could treat your SUP pumping as cross-training

(I get my 12'6 up to 14-15psi in 3-4 mins, another 4-5 mins to get it up over 20 with the standard pump but it's a workout...high pressure hand pump is slower but a but easier)
Edit: what brand of SUP/pump do you have? Not all pumps are the same...the one that came with our RED Air is very good, the one that came with our Hobie is a POS.