I thought that WAS a 1/144 stage (S-2 stage specifically, Monogram did their kit in 1/144 like Airfix and Revell's 1/96 Saturn used wraps for the stage bodies). Only smaller stage I could see to slim the size down a little would be 1/200 from the AMT Man In Space rocket set, but I don't believe that would be small enough (1/48 perhaps).
Of course, one could try starting with a Revell Mini Vader's TIE for the wings and cockpit window (since it is close to 1/72 and since MPC Vader's TIE wings were used to make the TIE Bomber) and maybe try and scrounge some tubes in that scale to scratchbuild the body. The "scale" of the TIEs is somewhat up for debate among modelers, but if one goes by the LFL measurements, the MPC Vader's TIE kit is about 1/35, so if TIE Bomber variants (including the shuttle TIE) go by that as well, then 1/35 would be the "studio scale", or at least within the ballpark. To get one close to 1/72, one would essentially have to use a 1/288 Saturn V model and I know of none that had all the parts needed (Aoshima's is way too small and the prebuilt one I've seen listed as 1/288 is closer to 1/300 or smaller). More elements would need to be scratchbuilt, but I think it would be possible with the Revell Mini TIE parts.