I've got a fix that looks like like it will work. I took off all of the goo with Goof off. I also took off the waterproof tape, but you should keep yours on since this fix will work with that still on. I took double sided tape, but I used the kind that has a bit of spongy center to it and not the thin stuff that you would find in winterizing film for your windows. Get Scotch brand Indoor/Outdoor Mounting tape (super super sticky!). you can find it in Michaels by the picture framing stuff or at Homedepot/Lowes. The reasons for the spongy in the middle are A) it will pick up the slack caused by the streching of the rubber band and B) it will enhance the tactile feel of each button push. The tape I got is 3/4 of and inch thick. I had to trim it a bit to fit so you may want to try a narrower width. I peeled off one side of the tape and wrapped it around the whole unit and cut out holes for the buttons. You may want to get creative and use a small hole punch for this part. Once that was done I Peeled off the other side and positioned the rubber band on the unit being careful to line up the buttons with the holes. Once it's on you'll notice that the slack is taken up in the formerly loose rubber band.
One thing I did note about using this tape is that the rubber band will not stick perminantly to the tape but it wont move around either. The tape is tacky enough to hold the band and takes up the slack nicely. When pushing the buttons, you get an enhanced and positive feeling press of that button since the buttons sit higher up. I think they feel better than when I bought it new.
I should mention is that the rubber band on my unit ripped in half at the bottom of the GPS where the lanyard hole is but this technique worked for me even though the rubber band is not connected all the way around. I will try to come up with a way to mend that part and post what I come up with here. I hope this helps everyone who's felt cheated by what Garmin should have fixed years ago.
-Dr. Witty