You can make a basic sphere jig fairly simple project if you have some basic metal machining tools to work with. I have fabricated 3 different
sized jigs for the wood lathes I have in my shop, All of them use the same basic components, the only difference is the height of the post
that holds the cutting tool so it aligns with the headstock spindle height. You can search eBay they show up every once in a while, you might
also look at some estate sales, there are plenty of boomers making their way into retirement homes over the next decade or two.