You do have a large number of choices if you don't mind a single battery box mod being TC capable.
There's the new Pico which has a single 18650, for low budget needs (full disclosure, I didn't care for mine, but lots of folks love them) and then things like the Jac-B which is a lovely mod and has great TC (that you don't have to use) but it is pricier. Folks do think it's well worth the price however. If you want a rugged, indestructible mod there is the Geekvape Agis one battery mod, that thing is really for industrial applications but most folks enjoy the vape. If you want a single battery without TC, you can't go wrong with a radius (if you don't mind charging it via USB, which is really recommended) that and finding one for a price that won't knock your socks off. It's a great vape, no TC, but it's really not a "switch out" type of system, it wasn't designed for that. Hmm.... What else? The Hohm series of box mods are super functional and do a LOT for the price, people tend to love or hate them though, and more for their capacities than hand feel, necessarily....
Other than tube mods, most of my box mods have two batteries, that may be more than you want/need but having that extra battery life can be nice. If you are looking for more portable, smaller options, well they are out there, and you are getting some good suggestions.... I'm sure they'll keep coming...
Good luck finding something you like.
Anna