After poking around a bit, I wound up on McMaster Carr's website and found these "Oldham" type, zero backlash couplers. They're only 1/2" diameter with a 5/8" stack height. They only had acetal or nylon discs available, so I got the nylon, but teflon would be better IMO. Either way, they work pretty good and are pretty smooth if you need something small. I made the mistake of braking a cabinet before I had components, and should have left more room, but it all worked out.
PS, don't mind all the overspray, I used scrap aluminum because it was cheap, but it had to be painted and I hate painting.
PS, don't mind all the overspray, I used scrap aluminum because it was cheap, but it had to be painted and I hate painting.