Hi ive got a set of high back seat and im wanting to cut a set of holes for my harness can you buy the plastic inserts to place in the cut holes

If they are like the cobra leather padded kitcar seats, i'd talk to place like cobra and see if they can send them. Although first point of call might be ebay.

If they are fibreglass seats it might just be possible to use rubber edge trim? or again use a cobra insert