you can't buy it, i have made it myself. But since all the plans and schematics are
made available by the M.E.G.A Team, it wasn't to hard. (only time consuming, i.e. getting
the C65 keyboard connector, but if you need the c64 keyboard connector only, it's easier)
see here: https://github.com/sy2002/DM65PIC
soldering the ATmega onto the board was a pain in the a.. as well.
So i would suggest, plan some time for building.
the only thing i had to do was changing the pcb layout slightly, since the PCB manufacturer
wasn't able to get the MEGA65 logo at the bottom of the PCB. (Some error with to high resolution). So i have glued the MEGA65 logo afterwards onto the board :-)
here is a link to OSHpark, who have done my pcb.
It costs roughly 120USD for 3 boards (3 boards is minimum order)
If you have questions or want more pics, feel free to ask. i am happy to help.
Last word: if you can't wait for the motherboard MEGA is doing at the moment
and want to hop directly into the project, make your own DM65pic board.
Otherwise wait a little longer for news from M.E.G.A !