I found plenty of options, you probably want 23-25mm pvc heat shrink, searching for "23mm pvc heat shrink" gave me plenty of results.
Here's one of the first results on US Amazon https://www.amazon.com/Othmro-0-91inch-Flattening-Insulation-Industrial/dp/B07VZLN52Y/ref=mp_s_a_1_4?crid=3S7GALSRMFY1I&keywords=23mm%2Bheat%2Bshrink&qid=1685099815&sprefix=23mm%2Bheat%2Bshrink%2Caps%2C215&sr=8-4&th=1&psc=1