If i found that i had no gas and all I could get was a small canister, then i would have two choices, have what i could get or do without!
To be honest, this is all included in what i used to call boat husbandry, or in otherwords, common sense.
IE check there boat before leaving and note what you haven't got and ask yourself, can i do without it on this voyage. Things like Canal guides, water, gas and a hundred and one other things that are needed in this pastime of boating!
common sense.
The OP started this thread on Sunday evening, it's now Wed morning, surely he has gas by now?
Nipper