QuiltE

Remember it needs to be reversed on fusible to get it the right direction, so trace it directly onto the fusible without the reversal, and that should do the trick for you!

If the lines of the original are not dark enough to show through, the layers go over with a heavy marker first.

My lightbox is an old drawer with a piece of plexi on top with flashlights in the drawer for the light.
Not likely you have a drawer as big as you need for your 26"... but could you not do the tracing in sections, by carefully laying it on, and shifting the placements of the original and tracing to do the next section?? Painter's tape would do the trick to hold both in place at each stage, and would peel away without damage.

In light (yes, pun intended) of the non-existent window at a safe level .... what about taping all to a glass shower door, and turning on the light? If not enough light, set another lamp inside the shower?

Or head on over to Staples or any good instant print shop and they should have the equipment to do the job for you. Oh wait ... what about your employer???