I'll tell you exactly how to do it, I did mine recently.
Buy a motorbike inner tube like this, I got one from this seller.
http://cgi.ebay.co.uk/21-inner-tube-motocross-crf-kx-ktm-sx-yz-rm-rmz-yzf-cr_W0QQitemZ8020102175QQcategoryZ21669QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Cut it through so you've got one long tube with the valve in the middle.
Slip each end over the places you've indicated, clamp it down and then inflate a little.
With the rubber tube rigid you have to wrap it totally without any gaps with duct tape.
Two layers is better.
You can now pump it up to 1.2 bar.
Failure to wrap it with tape properly will result in it bursting with a loud bang!
( I know from my first attempt)
You can just test the pressure with a gauge to see if it maintains it.