I have been looking around for large PVC bags to cover my swag, tents, charcoal etc. After seeing prices for over $300/$400 for bags over 2 metres long and 1/1.5Metres wide, I found a cheap options, - Kmart air beds.
For the long narrow items I brought the $20 blow up beds from Kmart and cut the insides out. You can cut them up to make smaller and use glue (
http://www.afdaustralia.com.au/glue/) to glue it together. I can put the Blackwolf Turbo Light 300 in this bag.
For the large items you can use the double/queen beds that cost $30.
I plan to use the queensize bed one and leave the sidewall on of about 200mm to put over my bed in the camper to keep it dry and protected.
If you want to make a dry bag just glue nylon webbing with ladder clips and you have a dry bag.
Make sure you turn it inside out so the felt doesn't get wet.
