I’m forever looking for replacement parts etc. I found KATO part numbers for my passenger car trucks. Parts 800033 and 800043 are the silver ones that match my ARR set. I found them available for purchase on https://www.n-scalemodeltrains.com. They are Boston and Albany Hobbies out of NH.

836 Candia Road

Manchester, NH 03109

(603) 305-5023

Kato catalog #800031 (Smooth Side Passenger Truck, Black w/o Coupler, 1 ea)
Kato catalog #800032 (Smooth Side Passenger Truck, Gray w/o Coupler, 1 ea)
Kato catalog #800033 (Smooth Side Passenger Truck, Silver w/o Coupler, 1 ea)
Kato catalog #800041 (Smooth Side Passenger Truck, Black w/ Semi-Automatic Knuckle Coupler, 1 ea)
Kato catalog #800042 (Smooth Side Passenger Truck, Gray w/ Kato Knuckle Coupler, 1 ea)
Kato catalog #800043 (Smooth Side Passenger Truck, Silver w/ Semi-Automatic Knuckle Coupler, 1 ea)
Kato catalog #800045 (Smooth Side Passenger Truck, Black w/ Fully Automatic Knuckle coupler, 1 ea)
Kato catalog #800046 (Smooth Side Passenger Truck, Black, Observation w/o coupler, 1 ea)
Kato catalog #800093 (Smooth Side Passenger Truck, Silver w/ Kato Magnetic Knuckle Coupler, 1 ea)
Kato catalog #800102 (Super Chief Pullman Truck, Silver, 2 ea)
Kato catalog #800104 (Pullman Passenger Truck, black w/ Fully-Automatic Knuckle Coupler, 2 ea)