I've got an old Crud rear guard but not the rubber shim that fits in the bracket to size it to the seat post.
I can't find any spares. It's an older version, but fits the bike perfectly. Does anyone know what sort of rubber/plastic Crud used for shims? Seems to be the same as things like bike lights. I'm trying to find as near a match as possible rather than bodge with electrical tape.
They appear to still be in business Contact
Personally I’d use a bit of innertube.
@woodlikesbikes what shape is it? if you can post a pic of your rear guard clamp I'll have a look in my spares box as I think I've had about 4 crud rear guards
@woodslikebikes if fazzini can’t find one it’s likely that I’ve got one, you need to measure the external diameter of where you want to fit it (I fit mine on the seat tube, not the post) and post it up.
This is what they look like! I know cos I have a few. I can draw (see Art Thread!) but only when I'm copying something, so this is the best attempt without having one in front of me 😆

(not a flying saucer!)
actually more like

As I suspected, 3 x shims for 27.2mm seatposts and 3 x for 29mm seatposts. If any of those work @woodlikesbikes drop me a PM and I'll post on.

You can use anything. I used to use cut up sections of an old innertube.
@fazzini - that's awesome! My spares box drew a blank. And is now all over the floor....
Sending you a PM.