The original uBITx design was published by Ashhar Farhan in March 2017. A number of people have built a uBITx up from scratch.
Richie KM4TLR has Eagle layout files for the RF sections of the UbitX if you are building one from scratch. He took a modular approach, so there are several circuit boards that you could make a UbitX or a single conversion design. The photos tell it all.