Tuning BSA Ultra MMC single shot seals needed

I am trying to find a seal kit or oring specs for my BSA Ultra MMC single shot. I have searched and found a vendor that lists seals for the Ultra but not the MMC specifically. I asked and was told the kit was for the new style Ultra. Rifle is a .22 12fpe version the original owner brought over from the UK.



Stock photo of what the rifle looks like.

6014EE0C-C9B5-4E3B-8EBE-B3775880F94F.1609608674.jpeg





 
I have the same gun, but mine is about 15 ftlbs. Also, I was under the impression that the seal kits for the MMC or newer ULTRA were the same, but I could be wrong. 

Was it Huma-air that you checked?

I could not find a BSA seal kit supplier in the US.

I needed a seal for the filler valve, but didn't want to wait for a delivery (I've been waiting over 1 month for a Probe from Huma-air). So, I looked up BSA seal sizes and bought two o-ring assortment kits for about $8 each and found an o-ring that fit and has worked for a month with no issues.

I think I found a list of the main seals & sizes on a UK airgun website. I can search it up if you can't find one.
 
When I ordered from Huma-Air, I had same credit card stop ... so I had to approved the charge with CC Company and redo the order.

But, as I mentioned earlier, although Huma confirmed shipment from Netherlands over a month ago I still haven't received anything. I'm hoping it's just shipping delays due to covid and Christmas.

Therefore, if you can avoid ordering from Europe it would be better.