Is it the 1 that screws into the filter housing?
If so I have 1 not sure if I can find more.
If your stuck I have a spare r o you can borrow.
Thanks, RZ, that's good of you, but no, it's sorted. For a short term solution I just reconfigured the RO pipes so the mains tap water goes directly into the RO filters (no pre-filtering) and then out via the DI chamber.
Obviously this'll lessen the life span of my RO filters, but it'll do till the order arrives.