Depending on what kind of hybrid you are looking at... try calling your local car dealers. For instance, most Toyota dealers in my area have a rental program. Not all of them have rentals available for hybrids, but it may be worth a try.

For Toyota, go to their website, and click on "locate a dealer". Put in your zip code, and it pulls up a list of dealers, and should also list what services they offer... look for ones that offer rentals.

I'm not sure if other companies offer this.

Good luck.