We are happy to launch our British Rail Tow Tractors in N Gauge which were so synonymous with so many mainline train stations.
These items would pull a variety of trailers however they would typically pull trailers with Royal Mail post bags or parcels and also the ubiquitous BRUTE trailers - https://en.wikipedia.org/wiki/British_Rail_Universal_Trolley_Equipment
They are currently available in Yellow with black wheels, seat and steering wheel.