When I was growing up we had two very large incubators for turkeys (together they filled a room). The candling table was a cut-out slit in the surface with a row of normal lightbulbs (1950s version) underneath. The eggs were in partitioned trays in the incubator, long rows, so candling was easy: you took a tray out of the incubator (well I was only in single age figures so someone did that bit for me) then perched each row of eggs over the lit slit and candled them, moving the tray forward as you went. It was perfectly adequate, with a business depending on it. My dad made it and he was not exactly the handiest man around.
I am thinking you could modify that, depending on how many eggs you want to candle, even having one for a single egg at a time. You would need a wooden box with a hole on top and a bulb inside, plus a darkened room.