Usually cheap 9 volt battery connectors that you can buy are flimsy and don't last for long. Here is a way to make yourself a battery terminal that will last. Oh, did I mention it's almost free?
You will need:
* dead 9 volt battery
* sharp knife
* soldering iron + solder + flux
* red and black wire
* a piece of heatshrink tube
* a thin ziptie
Step 1: Rip Apart a 9 Volt Battery
Take the pliers and rip apart a dead 9 volt battery you have lying around. You'll get a piece of plastic with terminals on it.
Using a sharp knife punch two square holes in the plastic
Strip and tin a couple of wires. Preferably - black and red. Note the polarity - the red wire goes to the "crown like" terminal.
Solder the wires to the terminals. Watch the polarity! Don't overheat while soldering, plastic tends to melt rather quickly.
Put a piece of heatshrink and heat it with a soldering iron or a lighter
Carefully bend the heatshrunk wires back and tighten a ziptie thru the holes you made earlier.
Now you have a proper 9 volt battery connector.