First post here. May as well be with a tool.
If you are a subscriber to little machine shop's email list, you may have seen an R8 collet carousel for ~$20. I saw it and figured it would be a good 3d print. The STLs are available at R8 Collet Carousel by degreaser - Thingiverse
It can hold 12 R8 collets. It uses a 3" 5/16-18 bolt, three washers, two skateboard bearings and a 5/16 nyloc nut.
I'll post some images of the printed carousel later.