https://www.bing.com/search?q=tradel...Tw=1&isAutoP=1
Scroll down to the Tradelink phone numbers starting with 8 and start phoning and asking the question.
Can I get one of these
Tradelink bought out Raymor some years ago
If that fails take the cartridge to your local plumbing supplies, as in life you may get lucky and find a cartridge from another mixer suits.
edited to add more info