Hello Wendell,
You can use smaller size AA batteries, They will give you plenty of detection (30 hours plus) per set.
Today's Alkaline batteries last a long time, And it reduces the weight a bit.
Two options here, I'll post both within a few days. I've used both options but prefer doing a minor mod and using the single 4 pack AA battery holder, You just need to solder in a 9-volt battery lead to the circuit board and then clip on the single 4 pack AA battery holder to the 9-volt battery clip. A 4 pack of AA batteries is 6-volts, Please don't confuse the 9-volt battery clip with using a nine-volt battery but instead use the 6-volt 4 AA battery pack otherwise you'll eventually fry the detector if you use to much voltage.
Gave me a couple of days and I'll post the mod, It's simple and using AA batteries is so much better.
Paul (Ca)