Well, since almost everybody has all the Christmas stuff out in the stores now, you can probably find some small, battery powered lights to use on your hammock and tarp now.

I mentioned this to my wife last year and she found a set of white, and a set of colored lights at Walmart (She thinks it was Walmart).
The colored ones used smaller batteries, so I took them on a couple of Scout camping trips and they worked well for running along the tarp, but not so good for illuminating the inside (White would have been the better choice there.)

Anyway, they both also got packed up with all the other Christmas light last January, so I have not used them the rest of the year!

DKPerdue