Other alternatives include:
QUICCO Sound mi.1
Zivix puc+
The mi.1 is similar to the Yamaha MD-BT01. The QUICCO engineers are ex-Yamaha and developed the mi.1 before Yamaha released the MD.
Two other new offerings are:
QH U-M8 wireless MIDI adapter
Frunsi BM-A01
They are also similar to the MD. Prices vary.
All the best -- pj