in my PFD i have one of those survival bivvys to get into and a good,not 99 cent chepo,foil blanket.the along with the thin foil blanket i have the cord and tape to make a rain/wind break.
in the same pouch i have a head net and packs of bug off.
i assume ditching the canoe and losing the gear would be in really bad weather so those items would be a good start.
i stay away from bad water so every having to use these is very remote however i now wear or carry my PFD on some of the long nasty portages.if i fall and can't keep walking i can "camp" on the trail until someone comes along.
the PLB i'm picking up will solve the major problems.

i should note that after reading the posts here for the last few years i don't head off for a bit of walk in the Mississippi river back water areas without putting a few things in my pocket i never thought of before like a whistle,Bic,small foil blanket and one or two other things.
i always take my SAK and cell phone anyway.