I'm going to try my hand at one.@DavidR8 you can mill your own, by drilling 1/16 holes at the points and cleaning up with milling cutters.... Janger made some for me for Christmas, out of 1/4" aluminum - they are beautiful! (3DP handles, too!)
It's a 9/16 which make a premade handle hard to find. But I'll have a go at making one.@DavidR8 - what is the size of your vise handle hex?