Check amazon, e.g. https://www.amazon.com/American-Black-Light-Fixture-bulb/dp/B0002F5544

It's often recommended to use a portable generator, but they can be a little expensive. I don't have any idea how to rig it to a car battery either, but that sounds bulky, and I wouldn't want to be carrying around a vessel sloshing with sulfuric acid in addition to a net and a backpack full of jars.

I purchased this blacklight for my setup, and it's decent for the money. A lot of people will recommend you get a Mercury Vapor (MV) setup, but I reckon they'll have a considerably larger power draw. Also, here is a link to the sheet that I purchased. It's a really good value, especially since it will get covered in various bug fluids.

Funnel trapping is also a good method, but I've never tried it personally. Let this post ferment a little bit, and I'm sure you'll get a little melting pot of information going!

Good luck!