My used late 80s Rega 3 came with a loose belt. It looked like a regular o-ring, so, knowing no better, I bought several from an engineering supplier after checking its diameter & approximate durometer, & choosing two or three with different circumferences. One fit the drive train & I was pleased with the result.
Many years later Rega's white belt came along & I bought one. I thought it was a significant upgrade until a couple of years later when I'd had enough of the bass getting soggier & the music losing its snap. The damn thing had stretched. I reinstated the old o-ring, & it's stayed ever since. The platter speed is accurate.
Until reading this thread I'd forgotten about the Reference EBLT, & I've been spurred to track one down.