Will you power your miniature walkie-talkie with a miniature nuclear reactor? Becase a tiny button cell watch battery might last only a few seconds powering the radio transmitter. It might last a few minutes powering the radio receiver.
Unfortunately I do not think that this will be possible unless you work at a microelectronics factory. It is something very few people will be able to ever do. what about buying walkie talkie watches?
I bought a walkie talkie in a watch 15 years ago. It transmitted about 25 metres and the batteries lasted about 10 hours. It had a separate battery (2) from the watch. It just used surface-mount components and a piezo diaphragm for the speaker.
I can talk to a person who is only 25m away. Why bother using a walkie-talkie?
My small FRS radios fit in my hand or in my pocket, have a range of at least 0.8km and their rechargeable Ni-MH battery lasts a long time before needing recharging. They were inexpensive.