1trackmind
Your UCD-100 uses a Sony KSS-213C laser easy to get and cheap, pay a little more and get the whole mech assembly and laser, it’s easier to fit.
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR4.TRC2.A0.H0.TRS0&_nkw=KSS-213C&_sacat=0
Cheers George