Hi, um I feel stupid now... I can't remember the technical name for it. Anyway, the red filter that swings under the enlarger lens so you can focus with the paper on the easel. Can you buy them separately? I have a Fujimoto enlarger that has the holder for this filter but not the filter itself. The filter holder is hardly a miracle of modern engineering - it's just a metal ring; no screw thread, nothing except for a couple of tiny 'bits' sticking out presumably to hold the glass in. The LPL enlargers I'm used to using have a 'proper' filter holder; this sees to be simply a receptacle into which you stick a circular piece of glass. So I'm not sure what I'm looking for here - just a red piece of glass the right size to fit in the holder, or something more specific? Thanks in advance.