I ran into this a few weeks ago. Just wanted to do a drive around Mt Rainier on my overnight.

Whatever you do, resist the urge to use the discounted companies like Fox, etc. Just look up Google and Yelp reviews, or ask me about my experience with Fox in FLL.

Be careful with the name your own price as well. When your price gets agreed upon, your credit card gets charged. If you're non-revving, etc, and run the risk of not being there, you could end up eating the cost.

Travelocity, and maybe some others, have no cancellation penalty, meaning you can cancel at any time if you cannot make your non-rev, or if your overnight gets changed, etc. I've even no-showed with no penalty, but I certainly wouldn't risk it.