Boy, what a headache. If I didn't say it earlier, I found that the my air cylinder is the one Magma uses, 1 1/16" bore, 6" stroke, 5/8"-18 thread nose mount. I called Magma, and they were no help, stating they have been using them for 50 some years with no complaints. I've been trying to source a 1 1/2" or 2" bore cylinder, but they all seem use a 3/4" or larger thread!
A simple fix would be to use more air pressure on the one I have, although I don't seem to have a tank with a safety relief over 115 psi. I doubt the extra 10-20 PSI would make a difference.
I have been reading of bypassing the air cylinder altogether, and just pressurizing the lube tube straight through the cover. I might have to give this a try. Edit: scratch that, it looks like the lube tube ID is also about 1 1/16", so nothing to be gained.
Unfortunately I do not have all the parts for the manual lube screw. I have the spring/seal assembly, and the handle, but it looks like I'm missing the screw itself, as well as a spacer that goes between the screw and spring. I found a 5/8 fine thread bolt just so I could try it, and it definitely works fantastic compared to the air cylinder. Magma wants an outrageous price for the parts, and I can't see any on ebay. If push comes to shove, I might just try and make it work with a bolt.