Gate access keychain A23 battery

I've got my home territory gate access keychain. It was designed to be compact, so it used A27 (MN27) type 12V battery with low capacity. This is quite expensive battery, also sometimes it is hard to find such rare battery in my location. I found the replacement - A23 (MN21) type 12V battery with much higher capacity, lower priced and wider distributed. It has the same length, but 10mm diameter instead of 7mm for A27.
I did model of the new keychain than holds new battery type and the electroni