The casters used on the 920 case are “quick change” removable. When the case is originally shipped the casters are inside the case under the aircraft. The OEM casters are plastic, not metal and therefore not robust. Great for rolling around the house but not up to withstanding the travel stresses of airports and train stations.
Rivets are not difficult to drill out so you may want to take that route to replace them. Done correctly, drilling out a rivet will leave a hole the same size as originally made for the rivet, allowing the same installation method and rivet size to be used again. A common drill bit size for rivet removal is 0.125”, or 1/8”.
As the 920 case is a design in common use across the music and entertainment industry you might try checking case sources serving those groups for replacements.