Yes there is, it's MEK.
For pvc use MEK (Methyl Ethyl Ketone) as surface prep. Go to your local hardware store and they should have some. It costs a lot for a small amount, but if you have a pvc raft, paco pad, then buy a half gallon or so.
Go to the local 'fabric' store.. you see mostly women in there (bonus!!) but there are some rolls of 500 denier pvc fabric available, which costs about 10 bucks per square yard. Get a foot or two of the color that matches your shit. They usually have a couple colors available.
Clean your surface with MEK, maybe three inches radius around the hole; On your drybag do it on the inside, so turn that fucker inside out. Cut your patch, set it on the cleaned surface. Take pencil, mark a key (one inch mark half on the patch half on the other material to orient the friggin round thingy-dingy), AND while you still hold it down as if it were final set run the pencil around the patch. Put glue on patch and inside circle, wait 15 minutes for glue to bond to fabric, stick together, heat the thingy with your heatgun for a minute and voila!
Good as new drybag, tada!
.. just a thought or two.