Been thinking to buy myself one for Christmas. What's a
reliable brand and type and model of carbon monoxide
detector?

I'd like a battery model, I can change batteries. But,
electric outlets are not to be found. All used up with
lamps, and such.

Whatever you do, get the digital. The squealing types go off when the CO is
high enough to reach threshold levels. Say it's 400 ppm. What if it's 390?
Wouldn't you want to know that there was some sort of a problem, and that
you were approaching critical mass? They have memory. What if the thing
goes off while you are not at home, but the levels return to safe before you
get back, and the squealer isn't squealing? You will have no indication of
the incident. Spend some bucks and get a good one. Digital. You are
betting your life and others on it.

Steve