Trophy, go to Wal Mart and get a Pool Noodle, one of those long foam float toys. Makes great scupper plug material. Cut off pieces about 1 1/2 inches thick, and slip them into the scupper holes. They will compress and seal nicely.
OK also makes plastic plugs for their yaks. Wild River Outfitters in VA BEach has them in stock to fit the Drifter.
Before you put them in it might be wise to take a pieco of shoestring and thread a loop through the center of the foam to make a pull handle, knot the bottom really big (to keep from pulling throug... use a coat hanger to make a jumbo "needle" to thread the string through the foam.) This provides a fast "drain" in case of a water level emergency...ie....lots of waves crashing over your boat, or biblical downpour....[wink]
I found a post somewhere that showed how to do this. I took a piece of 2" PVC pipe, sharpened the inside edge with a file and used it to punch out plugs from high density foam ( the kind computers come packed in). Don't use a hammer, just rotate the PVC pipe with your hand. I made a bunch in just a few minutes. Wet the plugs, compress them and work them into the scupper holes. They are absouloutly waterproof. You could then add the cord to pull them out, but I've found that I can push them out with my finger. The butt of my rod also works. They float, so you can paddle back to retreive them. Quick, inexpensive, almost unlimited supply.
I have a better solution. Go to Toys R Us or BPS and buy the little yellow or green balls that go to the little toy guns. They are little nerf balls and they fit the scupper holes in the drifter perfectly. If you want to be able to remove them while fishing you take an icepick and make a hole all the way throught the center and then force a peice of 150# floro or mono throught the middle, put an small washer on the mono then tie a knot, trim off the excess, bite the tag end flat and then put a touch of sealant on the mono on the washer side and then pull it into the ball. Make the mono long enough to go to the other scupper hole and use the other end for the other scupper plug. I have a knot tied in the middle that makes a loop and then put the loop over the base of my rod holder, that way when I pull them out they just hang on the rd holder and I don't have to keep up with them or worry about them flying out going down the road. Do the same thing for the back and then tied them to the seat rings. Hope this helps.
Going along with the little nerf balls, i had (before i made some foam ones,) been using little practice golf balls (yellow foam) they fit really tight in my tarpon, they sealed really well, are like a buck fifty at wally world for a dozen. (golf section)[wink] honestly i would still be using them, but i like to make things, and i had this nice peice of closed cell foam with no use laying around.......
p.s. they also fight really tightly in the bottom of rod holders, and are kinda hard to get out, so dont stick them in there....i dont know why i did, kinda like a kid with beans up his nose i guess...[grin]