I've found this thread and several others on here very useful in bookings some upcoming trips - as such I've registered and will add some info of my own info current as of summer 2019:
Horizon Divers Florida - Taught me the SDI Solo course and, obviously, is friendly to anyone with a suitable qualification since they are teaching it.
Scuba Club Cozumel - Did not object when I mentioned solo shore dives when booking. Anything in the Marine park must be guided per Cozumel law.
Red Sea Blue O2 - Claimed CDWS prohibits all Solo Diving (which is incorrect per CDWS's own website). I didn't bother to write back.
Red Sea Grand Sea Explorer - Fine with card. Mentioned it would be at the boat crews discretion and for some dives may not be allowed (having been there before, this is reasonable).
Bonaire Beyond the Corals - not equipped to support directly but did not object in principle. Mentioned rental pony's available from nearby shops.
It is worth mentioning that there are previous posts indicating Blue O2 is Solo friendly - apparently this has changed. Lying about it being a CDWS decision is completely unacceptable, however.
Anyways, hopefully this is helpful to others.