Typically your inexpensive "toy" grade helicopters have proprietary components that are sealed, so you'll need to consider something that's above the typical toy crap you find at Radio Shack or wherever.
HeliMax makes a very nice beginners helicopter that essentially flies itself:
And it has replaceable batteries. It is a "Mini" sized helicopter, which means you'll need a rather large open space to fly it comfortably (at first at least, until you are comfortable with how it flies), but it's a real genuine hobby grade Helicopter. There are replacement parts available too, as well as additional batteries. You will also want to get yourself a charger that can charge multiple batteries at once for more fun time.
Here are additional batteries for it:
A charger is going to cost you a bit more if you want to go that route, otherwise charge times are going to be around 1-2 hours.
My 5.2L Build thread
-1989 Jeep Wrangler 2.5L, soon to be 5.2L
-1996 Jeep Grand Cherokar 5.2L, donor and rainy day driver
-2004 Kawasaki KLR650 sunny day driver
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