There are many relay boards that will work. I used this 4 relay board from SainSmart. It’s connected to my Raspberry Pi and running my sprinkler system for 2 years. You can buy from SainSmart, I bought one off Amazon for a $6. They also offer relay boards with more or less relays, and also small signal and solid state relays – http://www.sainsmart.com/arduino-compatibles-1/relay.html