Alright, I got my pics of the stargazing IRS. It's a window on the upper fuselage behind the RSO, but ahead of the refueling receptacle. To make it look like a window or lense, I put a couple coats of future into the recessed area. Allowing the future to dry, this took a couple of days.
Hopefully here in the next week or so this Seattle weather will break and allow some outside pics in pseudo-sunlight. I'm looking forward to that, because flourescent lights are terrible to judge colors, tint and shading.