M_Boats: Fuse Holders

I hope someone can help me: I have a "87 Montgomery 15, hull # 389, that has an electrical panel built in. I don't know if it is a factory install, or a previous owner's work. My problem is that the fuse holders, red in color, have square heads and fit into a square hole in the panel. I broke a couple and can't find any replacements in any electrical supply house here. Does anyone know where or if replacements are available? Otherwise, I have to junk the existing panel and install a new one. Hopefully, one of you has a solution! Thanks! Bill