CMSNL is good, but can be expensive. David Silver Spares
https://www.davidsilverspares.co.uk/ have quite a good supply.
Agree on CMS, plus they sometimes maintain an odd practice to "inflate" shipment costs by splitting an order without notifying... sticking me with 2x FedEx fees...

They'd further rebuild/changed their http system recently, deleted the [my motorcycles] bookmarks in the process and show the fiche now alphabetically, which makes no sense...
Previously I'd select [my motorcycles] and just click on the vehicle in question (had 5 models in my account), now I have to wade through the
full search e.v.e.r.y. time...
As the UK decided to leave the EC and sail into the Atlantic, I can't order at DS anymore as customs get all over me...
plus that DS sometimes just decides to ship pattern parts whilst I definitely ordered OEM... not cool...

And their constant fuss in processing non UK credit cards; every time I had to call up and verbalize the number + 3 digit code to them...
I would even have paid via online banking, but UK refused to join that IBAN & BIC system from day one...
Wemoto would have been also a good source for pattern parts... but based in UK again the customs issue...
MSP is another shop, and they ship from within the EC, hence no trouble with exorbitant custom fees, they won't have the lowest prices but this might be compensated by lower shipping fees...
My procedure: verify the P/N in the CMS fiche, copy that and google the heck out of it... and always compare prices
including the to be expected shipment costs...
And sometimes you still can get really lucky and nick some NOS (new, old stock) parts at eBay...