I just made one. Because its challenging to solder six wires (3 per MIDI in and out) to a tiny 6-pin MINI DIN connector, I decided to just splice two MIDI female cable ends to a PS/2 male cable. I used these:
Two MIDI female cable ends
A PS/2 male cable end
Total cost was $12.86 (with tax and free shipping). Singular Sound’s cable is $21.60 (with tax and free shipping from Amazon). I could have made one cheaper if I bought raw connectors and wire from an electronics distributor but, like I said, its challenging to solder and wrap six wires to a tiny PS/w male connector (and my eyesight isn’t what it used to be). Using cables with connectors already attached will give you a more-reliable result.
Result: It took me a bit more than an hour to figure out the wiring diagram from the manual, solder all of the wire splices, and shrink wrap everything. I ended up with a nice cable that I trust to not fail. But I only saved $8.74. So, unless you really enjoy breathing solder fumes and don’t have anything better to do with your time, buying the BeatBuddy MIDI cable is a good deal in my opinion.