Please could anyone help regarding the damaged screw that i need to replace on my sight? it is the one that goes where the alenkey is any help would be appreciated.
I don't own one of those sights but it does look a lot like a 3mmxM3 grub screw - the same sort we use in RC car racing to lock pinions onto motor shafts.
Cheap as chips on eBay or via a good uk dealer such as ModelSport:
Another way to lock the sight aperture is to screw a nut onto the end of the threaded rod and tighten it up to the block. 8-32" is the thread of the rod. If they aren't readily available, M4 nuts will fit and they are much easier to source.