Show us a pic of the tap thread.If it's just a normal 3/4 tap thread then just buy what i showed above but both ends female and use some ptfe tape to seal it.
Copied and pasted......Where an extension attaches to a pre-existing outbuilding,
the pre-existing outbuilding becomes part of the enlarged, improved or altered
dwellinghouse; as such the conditions in A.1 (i) apply, i.e. the resulting extension
cannot project by more than 4m from the rear wall...
I have used them many times on that type of cartridge you linked above and they have worked a treat.
Type this in the search box on ebay. If they don't fit you have only wasted £3.50.
New Valve Tap Replacement Ceramic Disc & Silicon Washer Gasket Insert 1/2'' UK