If its canvas type material you can get a variety of sealers from a caravan/camping shop - spray on; wash type etc - none will probably be 100% but worth a try.
Buy a canvass waterproofer from any camping shop much cheaper than the same stuff from a chandler, cannot think of any product names but sure the shop will help maybe "Fabsill"
Fabsil is a silicone based product. The traditional wax based water proofer is "Mesowax" if it still exists. If it does then it should be available from good camping shops. Sould be available in various colours but they usually just stock the colourless one.