Your best bet would probably be to look around on Chinese sites like AliExpress since it's a standard proposed by Chinese manufacturers. The cheapest option would be a interconnect that adapts from a something like a 4.4mm to the 3.5 balanced. I found this one after a quick search that lists "3.5mm balanced" as an option, the the image looks like a regular 3.5mm ¯\_(ツ)_/¯? Probably message the seller and ask for more details before buying anything if the listing doesn't explicitly say it's a 3.5pro.
https://a.aliexpress.com/_mrwragO
There was also this cable I found that lists "3.5mm balanced" as an option but has no pictures. It's also getting pricy.
https://a.aliexpress.com/_mLB3e8q
Since that's a rather rare connector type most custom cable shops (Hart Audio Cables, Periapt, etc) aren't going to have it as a standard option, but they might be able to do a special order if you message them and ask. Most of them are pretty easy to work with but you might have to wait a while depending how backed up they are with orders.
Sorry I can't say "buy this cable, it works perfectly" but I think you should be able to find something that will work with some digging in the right places. Good luck!