I went the cheapie route on my original keyboards and bought $19 Linkworld LK-1000 models. They're 27MHz and dirt simple to setup one kb with all 5 receivers. Very reliable once you weed out the bad lots off the shelf. Just don't buy any bluetooth ones as those will NOT multicast from one kb to multiple receivers. You will probably have to buy 5 of the exact same model as they're all tuned to work on a specific frequency and data stream.