Found it in TC3, it's the Texture group for Stanier 8F bogey <kuid2:44090:57078:1> and a TC3 builtin - Also used for the 5MT and 9F in TC3
Think you must have the TC3 version of the 5MT for which you would need TC3, the later Settle and Carlisle version would need Settle and Carlisle being owned, if you have that then you need the loco from the Settle and Carlisle site, both sites are very similar but different!
TC3 runs in Windows 11 which was a surprise!