Combat Models offers C-141 A and B models for US$44.95. Be warned that "Combat Models" is not a brand name; it's a description. Most of their kits are very basic, essentially hollow shells with neither details nor decals. This vacuform modelling at its most primitive. The website mentions detail sets available for another $20, but does not say what's included in them. Perhaps you could enquire?
That Anigrand can sell their C-141 for the price it commands says much about the frustration levels of building a Combat Models kit.