For the Jerry cans and Propane tank, you might check out Amazon for BBQ covers and patio furniture covers. I want to cover the front box on my trailer and found a 'made to fit' patio table size for cheap. They make dedicated propane tank covers, $10.99 and up
(pictured is the $10.99 one).
It appears most of the US commercials Jerry can cover
($100ish) are all open at the top so that defeats the keeping dust/weather off.
The Aussies make fully enclosed covers in that price range.
You might see if you can find a surplus military cover for 'water cans'. They are fully enclosed and insulated.
If you are running 35" or below, there are tons available, with a wide variety of logos or not. Amazon also has tire covers listed up to 42" with open bottoms that might work well with your deck.