I bought some replacement bearings from eBay for £20 the other day for the pair. Seem good value and we'll made. Annoyingly the ones in there were fine, I thought they were rough buy it was grit behind the plastic bearing cover. Anyway, what might be useful to anyone is the maker and model in case you want to source your own rather than paying £15 each for them from hope direct.
Finesun Mr2437-rs
Finesun Mr2437-rs