I had never heard of XERO. But a quick search turned up an old BF thread that said they are Formula.
https://www.bikeforums.net/road-cycl...ngs-parts.html
There are a couple of XERO rear hubs on eBay, that my work as donors. If not, go to an LBS and see is they have a similar Formula made hub or Formula cones that match yours.
John