You can
buy this kit from PAIA, including the cool-retro case, complete with electronic parts, power supply, knobs, manuals. They even throw in the wires. You have the option of using a desktop case with wooden sides, or mount it on a 2u rack panel.
The price I think is also pretty reasonable considering that some of these things sell in the several hundreds.
The kit includes a burned EPROM (containing the programming). The code is also available on their website. And note, this is not just some analog synth that doesn't play with others... it has MIDI. It responds to note-on/off data, including pitch, velocy and gate. So you can hook it up and make it part of your MIDI studio.
Writeup from their website.
The FatMan has all of the features that give analog it's big bottom
and punch in a MIDI controlled package. The classic Voltage Controlled
normalization is brought up to date with a Velocity CV not available on
pre-MIDI synths. Pitch wheel modulation is supported and Pitch and
Velocity CVs and gate signal are provided on the front panel for
driving PAiA or other linear response synthesizer modules.
And all those knobs. They invite experimentation and invention in
ways that a single control with functions buried under layers of
obscure menus never can. Just a few hours with the FatMan will teach
you more about the nature of sound than you might ever learn otherwise.
It's as at home in the physics lab as on-stage.