BSA Single Shot Loader/Tray Issue

I was shooting in a FT match yesterday and and within the first couple lanes I started having problems with my single shot loader. The brass insert you put your pellet into fell out. Luckily I found it. It kept falling out and at some point I lost the o ring. So my fist question is what size o-ring goes in there? My second question is keeping the brass insert in place. I guess glue it?
 
Looking at the xtx air video on swapping out the oring it’s obvious the brass insert is not meant to come out so I will glue it. If I can’t find the oring size I will just try some different sizes. You can get them from England but I am not ordering a five cent oring from England. Sucks it happened in a match as it cost me some shots screwing with it. Finally gave up and used my magazine at the end and managed to double load a couple times costing me more shots. Oh well.
 
Ya dont order the o-ring. You can go buy an o-ring kit at the hardware store or if you find the right size just buy one local. Sucks to have it happen during the match at least once you get it back together it shouldnt give you trouble again. Use a glue that will allow you to remove it again if you need to replace the o-ring down the road.