Why the NdeM Niagara 4-8-4s were never available in HO or O scale.
Having been in the hobby more than 60 years, I can't recall seeing any NdeM steam power modeled by any manufacturer. If Mexican steam models were produced, they would be limited production, brass items but, the market for them would be very small. In the past 20 or so years, there have been some models of common diesel locomotives and freight cars lettered for Mexican railroads but, the same equipment also replicated that which could be found on US and Canadian railroads.