500 watt power inverter installed under the hood. Could have gone bigger but this was an emergency purchase to run a fog machine and some accessory lighting today for a last-minute photo shoot with no access to electricity.
Drilled four mounting holes in the plastic fuse box cover just in front of the battery and used the screws that came with the inverter to mount it to the cover. The inverter came with positive and negative leads that had alligator clips for the battery ends. I wanted a cleaner, more permanent install so I cut off the clips and installed the leads with ring connectors directly to the battery terminals, instead.
Already tested with my 400 watt fog machine and a few other things - power load is right where it needs to be and it looks like this will fulfill my needs for the time being. If I need to upgrade in the future, I will.
Edited to add: Unit was $34.99 on Amazon.