Gents:
Two points to this thread:
Canadians did use AA Cromwells. Enclosed find a photos of a Canadian Grenadier Guards AA Cromwell in Holland (4 Cdn Armoured Div). I believe some major model company (Italieri?) just released one in 35th scale.
As for having models of 414 Sqn Mustang 1's built, you could try on
www.aircraftresourcecentre.com Lots of knowledge and Canadian modellers on there.
Al Davis