They are
Fingertech TinyESC from Canada. Super simple forward and reverse. No setup needed and very reliable. I get them from
Palm Beach bots to avoid international shipping. Usually are in stock.
Ferrite ring is a good idea! If it works, I'll make room. Since everything went 2.4ghz I've never had a radio glitch until now. Super odd since I've run the same esc/motors/electro magnet on the Hitachi excavator before to test the concept.