Thinking outside the box for a tripod, how about a surveying tripod from a hardware store? I have a bosch one which was under $100, and with about $10 worth of nuts and bolts, I have a super stable platform for my tracking mount.
https://www.boschtools.com/us/en/bos...70-hd-34306-p/
I have some pics of the finished product if you want.
Regards
Chris