Don't you think it could be easier to go oversize a little? You are welding anyway.
I have some SS tubing here, specs are 1.9" OD and 1.75" ID. Sturdy.....0.066-7" wall thickness.
At least I can tell you where to look if interested, my friend does metal recycling. I only picked up a short piece from him but he told me: railings from some school aquatic center.