You can make one practically for free. Obtain a free sample box of a Ulano product called "Rubylith" that contains ten cca 8x10 sheets of orthochromatic masking film (red, of course). Stack two sheets and you have a brand new safelight filter. Then build a totally light-tight box with a 25W or 15W of one of those banned and extremely energy-inefficient old bulbs, put a switch somewhere (cord switch is very practical), tape Rubylith on top and there it is - your first safelight!