I found this site in the US https://www.ereplacementparts.com/slide-bearing-p-451630.html that has the bearings.
Also https://www.repairtoolparts.com/jet-parts/jet-708015-parts-list
Jet are made in Switzerland see https://www.jettools.com/eu/en/home/ while you can download manuals I could not see any place to buy spare parts but it might be worth dropping them an email if Axminster customer services who are their UK agents can’t help.
