Not sure about Weaver plastic trucks, but their diecast ones are virtually impossible to find, and have been for several years. For some reason, the last number of years while they were still in business, Weaver seemed to have ignored making these, for some unknown reason.
There had been some talk that the new Lionel LionScale series (which are made from the old Weaver molds) would have improved trucks that would be Weaver-compatible. They're offered as parts by Lionel. Anyone know if they fit the older Weaver cars?