I don't know about the ones from Mark II Enterprises but I searched and found (a couple of years ago) one of the thermostat types mentioned in the seminar notes, checked the operation (opening and closing off the bypass), and installed it in my Mark II at the same time the radiator was redone. Unfortunately, my notes don't indicate which one I purchased.
Larry
Larry Durocher
1956 Mark II C5601429
1962 RR Silver Cloud II drophead
2006 Ford F150
2010 RR Phantom drophead
2013 Bentley GTC
2015 Lincoln MKT