If you are going to go the route of using a dedicated chip, for most chipsets you can get them mounted on a board with the antenna, ready for say a breadboard. I have a few of them myself that work reasonably well (Stay away from TI's CC2540 as you need a separate programmer for the unit)
I'll be more useful in a few weeks when I'm down south, as I'm ordering a few things there that are actually moderately related to what you're trying to do. In the mean time, there was a post a while back on here in which a guy was modding his HHKB to work with bluetooth, successfully. From 2011 or so? Iirc.