(I don’t know how you got that picture up to 7.3Meg.) Anyway, it looks like the same wheels as the pilot truck on a 4-6-0 Big Hauler ?
Bachmann’s Parts store has wheels that look like the handcar, not the trailer, tho it claims they are for both.
https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=69_144&products_id=561&zenid=9038jiktb52b43mbqgdhoeas32
Interestingly, in the same list of parts, there is a “Wheels-Solid Black (Large Scale - Handcar & Trailer) $6.80 Could be used as pilot wheels in G:4-6-0, G:2-6-0” Although they are sold out, as usual. Confirms my suspicion that the pilot wheels are similar if not the same.
Here’s the nearest thing to the 4-6-0 pilot wheels I could find on Bachmann’s website:
Ah - George Schreyer to the rescue:
I don’t have one handy but I bet those are close to the wheels you are looking for.