Epidiascopes where produced in Romania too. I missed one for about 40 Euros.
Since folding cameras could used 6 x 9 format it is quite ridiculous that no one (or allmost no one) in Europe made home use 6 x 9 slide projectors.
When slide projection came up folders were already more or less a case of the past. In any case rather intended for people taking a snap now or or then, having it contact printed, some special ones enlarged. A projector for 6x9 would hardly be a budget product, even in a simple form. Moreover, people projecting rather did so in larger number, which contradicts to the to the rather restricted approach.
(I would not be surprised if my categorisation causes some criticism.)