Oiyagai 3pcs 315MHz RF Wireless Transmitter and Receiver Module Kit for Arduino/Arm/McU/Raspberry pi: Amazon.com: Industrial & Scientific
Connect an RF 433 MHz Transmitter and Receiver to a Raspberry Pi - John's Tech Blog
433mhz Rf Wireless Transmitter Module And Receiver Kit For Raspberry Pi - Buy High Quality Transmitter Uhf,433mhz Transmitter Module,Cheap Receiver Transmitter Product on Alibaba.com
Build a 433MHz radio chat device — The MagPi magazine