Yeah, the scene has changed quite a bit. The few of us that have stuck with it have evolved with the times to bring modern tech into the Retro market, which is kind of ironic if you think about it.
But I like to build quality stuff and I've made some really good contacts over the years to help bring that modern touch to the retro goodness.
The controller board is one of RDC's design. It doesn't take just any Pot and make it work, it'll even take sliders. So yes, for a portable it's perfect. But...he's not making them anymore, at least not in a one-off situation.
The audio amp however is something I could provide for you. Yes, he designed that too, but I have some extras I could populate and sell you if you want one. Only downside is it's meant for 16 to 32ohm speakers, which most small 25mm mylars at 8ohms can't handle. You can get 32ohm speaker in 28mm from Mouser or Digikey, but they are kinda pricey.
He also just finished off a beautiful PTH08080WAH/WAZ regulator break out board so you don't have to half-ass wire the caps, resistors and I/O to the thing. Got some of those on the way too!