you want Mariine Goop
altho any of the "Goop" products work well
Marine Goop is a little more pliable
you can also thin it with Toluene
but you need to do so in a can or glass jar, mix with metal or wood
if you put it in plastic, it will melt
work with it in a well ventilated area.
Goop is awesome stuff.
you can use it to fix a million little things.
i.e. saddle tears, glue innertube to tears on canvas, etc...
you can glue a patch onto an inflatable
let dry for a day
thin some goop
and paint goop over patch
this will put the patch under goop, and be just about impossible to remove.
for canvas patches
just use GOOP straight from the tube
I use an old spoke, coat hanger, etc...
smear the goop around
try some on a trial piece on some cardboard or something, to get an idea as to how it handles, so you don't squish a ton of GOOP out from the edges.
even if that happens, its pretty thick, so you can just roll it up with a coat hanger or spoke.
it will dry and last a very long time.
I pulled a Cars-r-Coffins patch off of my messenger bag after 6 years.
yes, it will dry, and stay put, grab a pair of channel locks, and start pulling the patch off
you can also color it with paint
its widely used in the world of R/C gliders, etc...
my grandpa once knew the guy who invented Shoe Goo
pretty much the same stuff...
but how many people actually repair a pair of tennis shoes, etc...
so we ended up with about 100 gallons of the stuff
what did we do with it?
my grandpa bought a old yellow Navy surplus life raft, that was full of dry rot.
used the air compressor to keep it inflated, and painted it with thinned down Shoe Goo
talk about a fire hazard!