Ok, you don't use a light box very often. When you really need one you don't have it. You can't justify spending the money for something you might use once or twice a year? (Or every few years.)
Here's a quick solution. Find a cabinet drawer. This one happens to be at the end of my intake table.
You don't even have to empty the drawer. This one holds some of my templates and rulers but you could use a kitchen cabinet drawer as well.
For this light box you will need a piece of plexiglass large enough to go past the sides of the drawer. This is the plexiglass that I used to use when doing pantograph quilting from the freehand side of my machine. You will also need a small light as well. This light happens to be one I had.... can't remember for what purpose though. I remember buying it on the discount table of the hardware. I think it may have been an idea I had for getting more light over my kitchen sink at some point in time.