there's a lot of bottom feeder mods out there that take 18650 bats, muddy.
I'm not 100% sure about the lower end price wise ones but the ones I own/owned are the phidias feedimus, monkeyboxx, ali'i, reo grand. and there's a new modder out there called southpaw modifications, he makes both the artisan line and the masterwork line.
the cheapest one out of those is the monkeyboxx. Tomb makes them, they are a very top quality wooden bf and he gives you a lot of extras in the package, carrying case, extra bottle/assembly, battery and charger. He used to give an atty and drip tip but I think its the bat/charger now. They go for 110 last time I checked
I know that with the phidias, the modder, fono, has used cartos with his mod before, but don't quote me on that as I have never used cartos on any of my bottom feeders.
EDIT: Now that I look at your join date and post count, I'm sure you knew all of this and feel kinda stupid for posting. your probably looking for a cheaper bottom feeder mod, take a look at COV, I know bruce had a couple bottom feeders on clearance for less than 50 bucks but I'm not sure what size batteries they take.
Hope that helps.