- Remember that cotton or linen cloth and canvas can be waterproofed thoroughly with a mixture of paraffin wax dissolved in kerosene. British clothing manufacturers such as Barbour and Belstaff have been using this for 100+ years. Oilskin waterproof sailors gear used the same compound.
If you do not want to try and make up this waterproofing yourself then the Barbour cloth dressing is available on Amazon.
Messy and it smells but historically a VERY Effective waterproofing treatment. Otherwise many other waterproofers for gear are listed in Amazons "Sports & Outdoors" section. Just searchfor "waterproofing".