you need to make sure that the generator can handle the wattage you're throwing it.
Some generators rate themselves at their MAX LOAD which is not so safe to run at consistently, there's one which rates itself 800w but if you read the manual it's more like 650w...just be careful.
If you want to find generators just go to The Green Book and type in Generators.
They're very heavy, just to warn you first.
If you are looking for portable outdoor lights Profoto rents out their packs, alternatively you can contact me as nearly all my lights are outdoor battery packs.
Just to let you know, fuel generators are not as easy as it first looks to use.
First, you need to ensure safety in handling flammable liquids. Next, you should only use in a big open space as the fumes can kill you - hence you need long extension cords. They are heck of a noisy as well.
Also, these generators are doggone heavy and you better prepare to get one with wheels. Next, you need to think about how you are going to transport it, as a typical generator can't fit in a sedan car.
Finally, you need to ensure the capacity of the generator can work with your lights and not blow them.
If you're not looking to buy new because of costs, that suggest you do not use it often. In such a case, I will recommend you go for the Jinbeis rather than this whole generator approach. I had explored that idea 3-4 years ago and abandoned it after learning about the negatives of it.