Hi Arm Bands,
I got mine direct from BSA, FOC Give them a call, their website with contact info is www.bsaguns.co.uk
They are very helpful and efficient , mention that you're having trouble getting pellet probe `O' rings ( they do chew up quite a bit ) and they'll send you some FOC
HTH
Norm
PS the parts diagram in my original manual was way out of focus, told them and they sent me a perfect one. Trigger adjustment is covered in the manual.