Two been advertised for a while, if so open minded why not one of those? Been to look? Why an Appia?
https://www.carandclassic.co.uk/car/C1063371https://www.carandclassic.co.uk/car/C1029991"The obvious" is to bring one back from Italy, or go through someone who does that on a regular basis. If the request was more specific I'd look up the guy in Essex who's brought several Flavias back.
"Any series, any condition, commercials" is quite broad. I know of a VERY rare commercial that might be for sale, but it makes no sense to anyone who pays for metal work by the hour.
I think that Jolly Camper is still for sale, again makes sense only if you do your own metal work, and have the usual space to get round, and store all the bits off it, AND you also need a lot of height inside the building, AND tall doors to get it in and out. Lovely thing.
Anyone else see:
https://www.channel4.com/programmes/find-it-fix-it-drive-itReminded of it as they turned a Morris ambulance into a period transport for a bike. I also enjoyed the vintage Wolsley rebody.