Use Mister Glue's Instant Glue for repairs on vinyl.

It is a bit expensive to do broad strokes but for repairs or manufacturing smaller pieces it is tough to beat.

Mister Glue's Instant glue dries clear and flexible and is water proof. And it will not dry out in the bottle.
This makes is good for:

Vinyl tarps and accessories, straps,
Hypalon - raft repair, vinyl raft repair - pinhole leaks, strap and ring repair and replacement
Kayak repair, inflatable boats, rafts and dinghies of all sorts.
Boat - Marine - repair tears in clear vinyl windows, vinyl seats, pvc
Swimming pool liner - repair tears and pinhole leaks
Automobile - clear vinyl windows, tears on tops, interior hard vinyl breaks and seat vinyl
Camping: Air mattresses
Inflatable Trampoline(more here)

Tip for repairing pinhole leaks in an inflatable raft or dinghy or air mattress: vinyl raft

If there is a removable floor of any sort in the raft, remove it. Blow it up hard and start spreading water with a bit of dish detergent in it and watch for small bubbles. Mark the spot with a maker but keep going there may be more. Often valves are the culprit. Make sure the O ring is good and replace if necessary.

Once you have marked all of the leaks deflate the raft or mattress and use a small patch of the same material using Mister Glue's Instant Glue. Use a large enough patch. If too small, it could come loose. Even though the Instant Glue sets immediately, full cure time is several hours. If you can, leave it over night.

To make the patch look less 'patched' cut to a shape of your liking. Make it look decorative.

If I'm out fishing or any kind of boating, particularly in something inflatable, I always have a bottle of Mister Glue with me. And some patches. Even a small tear can be repaired this way and get you back to where you started. Also, you can use Mister Glue to repair your lures as well.