I recently got a Panavise and saw some helping hands attachments, but they were more than I wanted to spend so I designed my own. For the arms I bought 10 flexible arms for about $5 at https://www.aliexpress.com/item/WSFS-Hot-10PCS-Round-Nozzle-1-4PT-Flexible-Oil-Coolant-Pipe-Hose-Blue-Orange/32773128689.html plus alligator clips. The only other thing I needed was 3/4" long 1/4-20 screws for the base (I couldn't find that length so I bought some longer ones and cut them down). The threads for the arms are modeled into the design. I first printed the ring with 0.2mm layers and no supports and it did kind of work, but wasn't clean. I then reprinted with 0.1mm layers and no supports and it came out perfect, the threads work great. I designed a total of 9 arm mounting holes which should be overkill for anything, but gives lots of flexibility. For now I'm using CA glue to bond the clips inside the nozzle holes, but that may need a better solution.
0.2mm layers did almost work, but the threads came out perfect with 0.1mm - use as small layers as you can.