I hope this all works OK. I am now hunting round to see if any other NG stock can be re-wheeled. Nobody has come for so far on the origin and availability of bird_d00's Simplex.
Afraid that Simplex has gone to Trainz Heaven, it was on the now deceased TPR Download Depot. bird_d00 was suffering from health issues a couple of years ago and nobody has heard or seen anything of him since. His Website still exists however the links are to TPR, http://www.lutrainz.com/other.html
Alternatively there is kevmt's Simplex, FR's Mary Ann which is on Trainzone not the DLS, I see you have utilised that at some point according to the DLS.
Another thought didn't nathanmallard have some miniature stuff at some point?
Then maybe the Rudyard Lake rolling stock which is 10 1/4" Gauge might possibly be usable, although I seem to remember they dug into the track!