Possibly worth mentioning Scott + Sargeant have locations in the UK, but also in Ireland (which is still in EU)
should that matter regarding postage to US, I'd think worth checking.
https://www.scosarg.ie/centauro-48-0...saw-spare-tyre
Parts-Pronto is where Eric mentioned in the past.

Indeed they have gone up since, they were fair bit less than half the cost a few years back, glad I bought one when I did, even though it's not very suitable for saws without the groove, I still got an insightful look at it.
Will likely make my own if need be, possibly with stuff like this, though could be persuaded if some other source was a better material.
https://www.ebay.co.uk/itm/SOLID-PLY...01&mpt=8060518


All the best
Tom