I have 4 of the largest ones of these
Marchioro Clipper Tonga Kitten Carriers etc UK each with a set of wheels and a shoulder strap (sold separately). My oldest 2 are now 10 years old and nothing on them has even snapped or broken and they were used every 2 weeks when I showed avidly. Although they come easily apart - great for storage or bleaching after a trip to a show or the vets, when clipped together they are very strong.