I thought brass might be the only option. That light gray scheme was only used for a short time. Dieselization had slowed during WWII and the dark gray was adopted in 1948. I have an MTH version of the 1938 20th Century Limited and I thought having a matching E-7 would make for an interesting option but I'm not going to the expense of brass to get it. I'm not good enough to custom paint one myself.
BTW they just flipped the colors. Original 20th C. streamlined passenger car scheme was medium gray body with dark gray stripe through the window section, separated by a blue (later white) stripe. A decade later the reversed the colors - dark gray body with the medium gray going through the window section.
BLI did E-units in N scale in the original scheme, but can't think of any plastic HO models in that scheme(?)
I've seen them in Brass perhaps from Oriental or Sunset but I do not recall any in the "reverse" scheme from the major plastic suppliers.
Challenger:
https://www.brasstrains.com/classic/Product/Detail/044576/HO-Sunset-NYC-EMD-E7-E7A-E7B-Diesel-Set-Black-DCC
There were two of the original four E7s delivered in black (4002-4003) with imitation aluminum stripes, these from Sunset:
NYC E74002_pilot by Edmund, on Flickr
Broadway Limited did an A-B pair in N scale as I recall but I do not recall seeing this paint on an HO version?
NYC E7 Manual_2 by Edmund, on Flickr
Good Luck, Ed
When the NYC first dieselized their top name trains, the diesels were painted in the same light gray livery as was used for the lightweight 1938 20th Century Limited. This paint scheme was kept until 1948 when the NYC adopted the dark gray livery. I have seen a few pictures of these but I have never seen it offered in model form. Does anyne know if this has ever been produced. I'm specifically interested in an E-7.