Hi Marvin, I built my own. A small block, chose a face. make a hole big enough to to take the shim and the top of the valve. From that face make a slot so that the valve stem fits inside. So now you have a cavity with a slot at the bottom which created a fork for the bottom of the shim to sit on. At the top drill and tap a 5mm hole and stick in a cap screw, this will push down on the valve stem head. Make the block the size of a spanner so you can tighten the cap screw.
So you place your collet, fit the mini press in, hold with spanner and tighten cap screw. Works a treat. You can feel the collet engage as you tighten. Sort of firm, firm, firm, loose, loose,firm, tight, type of thing as your turning.