I’m not sure if this is the right forum to ask but does anybody know if it’s at all possible to commercially acquire a much smaller version of a key fob? And if that’s not possible, the means to make a smaller chip that can emit the same radio frequencies? The application of this question come from my desire to put a key fob inside of a hotwheels model of my own car and mine not being small enough. (Pictures used to demonstrate desired size of Radio transmitter: something about <=3/4” W x <=5/8” L and with a depth of <= 1/4” would be perfect)

 

Could you show more pictures of the fob without the battery installed, and on its back?
Then comment on the idea of cutting of the battery half of the PCB and provide an alternative battery which can be detached and connected with a few wires. This might fit in the car.