that sort of thing. yes they are frrom time to time on ebay. just keep searching uk and international mine are all machined cnc alloy
I bought a set a few years ago. The round type are universal and easy enough to get but the oval are rare. They retailed for about £120 for the complete set. The oval cap is plastic with a long twin headed bolt. Don't think they're available now but you might find some old stock somewhere or s/h.
I have a spare CNC machined grey one which I bought from motorapido... I was told this was a DP item but cant find a part number for it... Both my sets are all aluminium... Including the oval ones.