Couldn’t you just try a bigger fish pump? I’m totally digging my Whisper 30-60 setup. Using an old 2x8 cylinder, silicone tubing from petsmart, and using a “T” inline (between cylinder & the pump), grapeseed oil as lube, and doing the thumb technique. I’ve gotten the hang of pumping up or down as slow or fast as I want dozens of times per minute even. Real easy to use and if I ever need more vacuum I’m just going to try a bigger Whisper or the like. Total cost (using an old cylinder I already had) was less than $40.
I have found a wonderful and cheap alternative since posting that, at post #119 of this thread,
$15 electric vacuum pump for anyone!
AND mo1258 has a wonderful post on how to set it up at post #136.
A word of caution is that this pump pulls a vacuum apx 20 in hg, so for safety set your regulator down to the safe range you are intending on using if you buy it.