Got pictures of that tubing you are talking about?
Sorry, no pics. But, got to a bicycle shop, ask them if they have a used inner tube from a 1 1/2" to 2" bicycle. They will give you a used one. Or, go to WallyWorld and buy one for $4.
I just cut a 3" - 4" length and trimmed it to clear the grip safety and to be clear of the mag well.
If you still need a pic, I'll try to post one after work today
Lots of Cast Iron to Cook With...
and a few defensive firearms, too!