I’ll build it myself. Take the stock one and follow that, then take it into a spring shop and have them heat treat it.
I cheat in that I’ll leave the end a little long and use a sliding joint to fine tune the sway bar. Just like I use on the race cars.

 

I'd love to see project pics along the way. Too much project creep for me, I got to get my car done and move on to others. You're gonna bend 90's in a tubular bar?

 

It’s no problem. I’ll use the same tube bender I used to build my roll cage in the XJS
have to buy a set of 1”dies though

 

That. sort of thing really isn’t needed. The stock suspension is excellent as it is. ( assuming it’s properly maintained)
Details like I mentioned comes from building race cars since 1962.