We use a 3/4" x 16 bolt for our Sherwood 17000 pumps. From McMaster-Carr (mcmaster.com) at about $12 each for medium grade and zinc plated.
I have both 3" and 4" versions. I also have the Sherwood T-handle (one handle end long than the other, actually, IIRC) but it doesn't swing well in the available area.
I started with using a socket in a standard ratchet drive, but swing space is limited, so...
In our installation, a niftier tool to use is socket on a battery operated ratchet driver. Ours is a Milwaukee 12V version that works pretty well. Another that maybe would be useful, but I don't actually have, is a ratchet-style box end wrench of the appropriate size to fit the bolt head (can't remember size).
Chesapeake Bay, USA