Hybrid Battery Charger?

Hey guys, I'm looking to use my 2008 base model Prius to camp in. I would like to utilize the electric A/C compressor so I can run the A/C overnight in the summer. However, I don't want the engine running on and off throughout the night. Is there just a plug I can use at campsites that I connect to the stock battery?
Just to be clear,
I want to still use the stock battery
The car would still be turned on so the stock fan will still be able to run
I don't think a high powered PSU is needed, just a low power pull to maintain battery level

Thank you all for any help you can offer! First post!

 

Thanks for your quick reply! Beside fuel usage, is there any downside to running the engine like a generator? As long as the internals stayed warm I couldn’t really think of a reason why it would be bad