It's a fairly old post from 2019 and several of us were involved with its development along with Erik. While it's made of parts that are readily available from EBay and Amazon it's not for the faint of heart because it was tricky to make it right with the filtering and position of parts. It took 4 months for Erik and the rest of us to realize the final design used with Erik's software. Several spinoff designs came from it too, but in the end Erik's design went to production and you can easily buy this on EBay as the TinySA for about $70.?
Marty Wittrock