I found CPC also had the odd AV03315 stock code as well as AVBELTxxx ones.
And that they also still do some round ones, with it seems 94 different ones in total (virtually all they have under 'AVSPARES' category). Plus either 'SoundLab' (aka Altai?) or Unbranded, but seemingly no 'catalogue' page linked to for these.
So after narrowing down the search to material=rubber, got this url to find them all:
https://cpc.farnell.com/w/c/audio-vi...t=P_PRODUCT_ID