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Vic can probably verify, but I think the Australian equivalent of Johnsons's 'Klear'/'Future' is called 'One Go', or something similar.
But as stated, any gloss varnish will do the job over enamels, although an acrylic varnish should be used for a model painted in acrylics, to avoid reaction with paint and varnish. (I still sometimes use gloss enamel varnish, over enamel paint, but finish with a mix of 'Future' and Tamiya Flat Base, to achieve the desired finish, from full mat to semi-gloss.)
I guess the only reason many modellers use 'Future' is because it's cheap, very cheap, compared to 'proper' modelling acrylic varnishes, and is versatile, for use on canopies and so on.