Although a bit dated this thread has a source listed and they appear to still be in business.
Last post is from the supplier
polished expansion tank elbow
The poster is listed as being from Ohio.
Dynamic Motorsports Listed in Ohio:
https://www.cityfos.com/company/Dyna...-OH-898169.htm
But the hyperlink points to Southlake TX now. Must have moved.
https://dynamicmotorsports.com/