Don't want to open your big tube of Polyurethane adhesive b/c it'll dry up on you in a short time and you don't need a whole lot? This is a very good polyurethane adhesive that you can use that comes in a smaller tube than the ones at the automotive stores.
I found it at Wal-mart in the sport and marine section. It's about $7 for this tube and works awesome!
Just passing it along in case there are some like me who hate to open the big tubes to do a small job and end up wasting a lot. This will dry up at the tip after 24 hours also, but you can cut the tube at the bottom and use the rest for later.