What kind of Lamp?

It's getting to be that time of year where houses start to get colder at night and while checking my BP's tank temps I noticed the cool side was at 70 and the warm side barely over 75. This was pretty alarming (she's been staying in her warm side) so I checked my friend's tanks (I'm taking care of his 1 yr old Female Normal and his Columbian Rainbow Boa) and their temps are also really low. Even lower than in my room because that side of the apartment is heavily shaded by trees all day and gets little to no sun.

What kind of lamp could I use to up the temps in the tanks? I know this poses a humidity problem but I don't mind having to spray the tanks 2-3 times a day and I am working on making the foil screen covers so they fit snugly on top.

I've heard about the ceramic bulbs and what not but am not sure on the wattage or where to position it on the tanks (the tank sizes vary there's a 10 gal, a 20 gal, and 2' by 2').

I do not have central air/heating and in my friend's room a space heater would barely fit. So any and all suggestions would be awesome.

You live in southern CA and it's getting cold? I prefer a space heater myself, it's what I have heating my reptile room.

It doesn't get "cold" until late night/early mornings and it's like low 50s high 40s which isn't TERRIBLE, but for some reason it's really affecting the tanks' temps already. Also, it's not sunny and warm here all day every day. It's actually been gloomy and foggy lately.

I wanted to avoid space heaters because I've had them in my room before and they've made me have nose bleeds. I have a very small heater thing (like a fan in the wall??? Had never seen one before moving down here) that's kind of close to her tank (but high over it so it wouldn't directly blow hot hair into her tank) so that might help in my room but in the other room it's far away from the tanks and I'm not sure how much of an effect it will have.