If you want the turret design pin, it seems your options are:
Buy the whole 4-piece push rod kit C24147 (at SNGB). This version doesn’t use the spring clip C27328/5Z that engages in a groove in the pin (as per S2&3), but instead has a split pin and spring washer to tension it. The Moss version of this kit C24147ASY shows a pin with a groove for the spring clip, but doesn’t show the clip itself, so it may not be included (see later).
Buy the C27327 pin (listed at Terry’s, Moss and etypeparts (UK) though whether they have stock is unclear). This pin is designed to use spring clip C27328/5Z in a groove on the pin which Terry’s say is no longer available. The SNGB web site calls the clip C273285 and says it is unavailable on-line, and suggests you call them.
Buy the S2 pin C29803 which uses the same C27328/5 clip according to the Jaguar Parts List.The Moss web site shows C29803 as in stock. I suspect that this option is really the same as #2, as the usuals say C27327 and C29803 are interchangeable.
The problem with options #2&3 is the clip C27328/5. No-one seems to have it, though if you enter it on the Moss site it then shows you C27328/3 which they do have. As far as I can see, the two clips are of the same design, but different sizes. SNGB also has C27328/3 by the way.
I think this may be a case where you have to pick up the phone and call each supplier. As often seems to be the case, there is some latitude being used when specifying parts as interchangeable (eg using a split pin and washer instead of the spring clip). It wouldn’t surprise me if you buy the turret pin with a groove, that will find that no-one has the right size clip. Maybe you can modify C27328/3 to fit, but I’d like to hear someone confirm that. Please let us know the outcome, so we can all benefit from your experience.