Trigger type?....
I think you might be using the wrong kind. The ones we use for these tubes have the trigger assembly all within the diameter of the bottle. So, I don't see why it would only fit in one direction.
Go to your local Walmart, they carry the PWC extinguisher that fits your tube. I just bought one this past year. They are pretty cheap, I think I paid $12 bucks for it.
I do remember seeing two different kinds. The one with the trigger, that had a finger ring was the same size in diameter of the body but the trigger stuck out. The other one, the one I'm talking about, had the trigger assembly that was mounted within the diameter of the body of the extinguisher so it would just slide right inside the tube........:cheers: