How to water proof my Oztrail Portaloo BAG

[albany_nomads]

Hi Folks
 I have one of these Oztrail cotton bags that holds our Portable Loo
Now with  our Coromal Mirage camper the bag and the loo fits very nicely in the opening of the A Frame draw bar ..as such I plan to make some brackets and leave the loo here whilst in transit.
But the bag while very versatile isnt water proof ,its just a cotton not a PVC. I can see it getting wet and grimy behind the Rodeo when towing the camper
Is there any thing on the market that I can paint the cotton material of the bag to make it water proof like a PVC.
 (can you get a pvc paint  )..just a thought

http://thumbs4.ebaystatic.com/d/l225/m/moB6HmuI_lFY_9XqxaxO-6w.jpg

A mob called River Rats make one

http://www.riverratz.com.au/html/riverratz_toilet_bag.html

just trying to find a cheaper alternative since I already have a Oztrail bag

Much appreciated,  John  /  Albany Nomads

[scarps]

You could try Selleys watershield, but might still need ongoing clean and recoat

[berlitza]

I had to do the backing on some pvc sheeting i purchased and used this stuff, couple of sprays and the water beads str8 off it..

http://www.ebay.com.au/itm/350304467052?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Not my products and im in no way connected with the company/sale

[cruisindub]

I thought those bags were canvas, didnt realize they were just cotton.?

Whatabout just a heavy duty bin bag/bin liner over the top.?

[KingBilly]

Mate, we have ours in a canvas bag exposed to the elements on the drawbar.  Dunny is all plastic so no worries with it getting wet.  If the bag gets wet, it dries.  If the bag gets dirty, it goes in the wash.  Life's too complicated 

KB