@shicks. I tested the converters you recommended and they appear to work as expected:
dropout voltage is 8 Volts and will support input voltage to 31.5 V (max on my bench PS).
No load draw is 3.64 mA at 12 V and 2.83 mA at 31.5 V.
A lower cost option is a three terminal non-isolated converter at $2.76 ea vs $12 for the PlusRoc.