Pity that so many of the main modelshops like Modelzone in UK stick to Airfix, Revell and Italeri and ignore Stretlets current products! If they were more widely available I am sure there would be the interest.
I would assume they don't stock them because they do not provide volume sales. I can't think of any other reason though you could write to them. I can always get them from F&S if I want them and if not in stock they will back order. Strelets supply fairly quickly to retailers if or when stocks run out.