Welll...SeaEra conversion kits for both sea water and fresh water were available, but no longer...and there's only one retailer who still carries the sea water conversion kit
Boatersland Raritan Sea Era Conversion Kit Defender has the best price for the complete SeaEra fresh water toilet (SeaEra QC), but before spending USD $600 PLUS another USD $150 for the 3 option "momentary control" flush panel" for the SeaEra fresh water, I'd go with the Raritan Marine Elegance
Raritan Marine_Elegance Promo.pdf which you can get for the same price from this retailer
Boatersland Marine Elegance Width shouldn't be a problem and neither should depth because the pedestal front-back is only 12.75 deep...the bowl hangs out in front of it.
Plan B: Unless you absolutely have to have an electric toilet, take a good look at the Raritan Fresh Head--the ONLY manual toilet designed to use pressurized fresh water.
FRESH_HEAD Promo Sheet About USD $400, which isn't bad considering the SeaEra sea water conversion kit is also $400 without a new bowl.
Or, you can see what Jabsco has to offer as electric toilet conversions. I'll be glad to help you sort out what's needed (solenoid valves etc) if you decide to go that route.
--Peggie