Step 5: Solder your switches/plugs
Solder a switch to a 9volt battery clip for the receiver .
The transmitter, if housed in a SMALLS tin will need a N-type battery holder, to save space no switch is included (I just put the battery in to turn it on) If you can't find a N-type battery holder you can simply solder the leads to the battery terminals then to a switch, just be careful not to get the battery too hot with a soldering iron or see if hot glue will keep good battery contact.
OR you can easily house the transmitter with a 9 volt battery in a normal size Altoids tin. The advantage of using a 9 volt will be apparent when you start burning through A23 batteries in 25 min haha.
P.S. the transmitter circuit also works with a "wal wart" power adapter if you wanna config your spy setup to plug in, you could invent a cool lamp or radio or something that has a laser transmitter in it that operates when the power is turned on or even use a PIR motion sensor to turn on your transmitter when people are in the room!! MUWHAHAHA