I have searched for years and tried numerous products only to see them let go at the worst possible time ie; out on the water . I guess it helps to know that a lot of glue and solvent containers use HDPE lids.
I have seen araldite, super glue, fibre glass and even rubber with tin riveted over it, soldering irons being used to try and fuse melted plastic in a crack, tar tape stuck over the split you name it I've had to scrape it off before welding and in some cases cut plastic away that was contaminated with gunk.
A quick fix is exactly that, and might make you feel good however how would you feel when your kayak starts filling up with water 2 klms from shore? if its going to break it will happen when its under the most stress, welding plastic repairs it as the weld becomes part of the hull.