Lots of great ideas being shared here. I've tried to hand-bend 1/8" steel flat stock for grill attachments before, and it didn't result in an elegant smooth curve like my imagination told me it would. I'm still not sure, however, that anything less than 1/8" would be stout enough for supporting the bowl. It will be pretty dang heavy by the time you get it loaded up with charcoal, a SNS XL, some cast iron, etc. Agree with the recommendation on fiberglass gasket - they make that in a flat variety (instead of a round fiberglass rope) that would work really well on that ring.
I've never seen anyone build out a Performer / Kettle Table frame using iron plumbing pipe fittings. Maybe that's an option? I could see someone making a beautiful table out of iron pipe fittings... that's a style that's very on-trend these days. Lowe's and Amazon also carry a line of structural pipe fittings called SteelTek in both galvanized and black finish. You'd still have a chore in chopping the pipe to length, but maybe you've got a chop saw that could work with that easy enough.
Excited to see how it comes along!