Inner tube has a great concept but the soft rubber can stretch and pop under alot of pressure. I found that you can use a metal bottle...
I'll explain it all in the tutorial.
(Note; I wont use real pictures just drawings to explain each step because of copyrighting)
Step 1: The Things You Will Need!
1. A metal bottle (preferably air tight and has a metal lid)
2. Tyre valve (car tyre valve)
3. Pumper with Pressure metre
The tools you will need are;
1. A drill
2. Drill bit set
3. UniBond all purpose sealant (extra security)
Try getting the bottle from Halfords. It's like around £5. The Tyre valves you can buy online for around £5. Four come in each pack) from sourcingmap.com. You can get a pumper from a car/ bike shop. and the unibond from a DIY store.
Step 2: Drill a Hole in the Bottle Lid
Step 3: Plug in the Tyre Valve
Step 4: Finished Cylinder
Then fill with air using a pressure gauged pump. The air will start to get compressed in the cylinder. Because of how rigid aluminium is compared to rubber, it will not pop under extreme pressure.
If you are still worried you can just make a case for it to keep it secure.
Step 5: Finished
(Working on a Video Demo.)