Well, I broke down and bought the new Samsung duo charger at Best Buy for $85. It's the new 2019 version that is completely flat and more compact, whereas with the 2018 version the phone charger part stands upright diagonally. The new 2019 flat version that I got has a higher voltage for the phone charger part of the device. I've used the charger for a couple days now and it appears to work well. I keep this new charger at home to charge up my S9 phone and 42mm Galaxy watch. The supplied OEM Galaxy watch charger is now kept in my backpack on the go or to be used at work.
The only minor nuisance about the new Samsung duo charger is that I can hear the fan come on when the bedroom is completely quiet. Granted it's a very quiet noise, but I don't want to hear any extra noise whatsoever. So to overcome that, once my phone and watch are fully charged, I take both devices off the charger (or move both devices a couple inches off the side on the charger so they don't register for charging).