Just bought an Extron RGB-HDMI 300 (A) that handles VGA and other RGB type signals and has HDMI output. I've connected it to my VAXstation 4000/60 (very successfully), and my IIgs (reasonable but this is at the low end of what the unit can manage). Output on either my Sony 46" TV or Apple 1600x1050 monitor. Found one (pull from service) at surpluscrestron.com for $53 shipped. It didn't come with the power supply (12 V @ 1 A) and needed this connector (https://www.digikey.com/product-detail/en/molex/0395000002/WM7732-ND/1280583) to attach the power supply.