Try a Google search for "superformance cv boot". I got about 30 hits from this forum. (Google seems to work better than the search engine on this site btw).
Several threads describe the metal bands loosening allowing leaks. (hopefully that is your case). Other call out PNs for replacement boot etc...
From what I read the early cars uses a Thunderbird IRS and Inner boot is OEM. Dorman makes a split boot (solvent glued)
https://www.rockauto.com/en/catalog/...613,drivetrain
Outer is SPF made and Olthaff racing seems to know the boot PN its said on the forum threads .
http://www.olthoffracing.com