I recently acquired a later model (1980-ish?) HP 8558B spectrum analyser plugin in its HP 182T display unit. It works, but the Reference Level control is missing components: a spring (45), washer (63), circlip (48), pointer (44), and index disc (47) as shown circled in red in the exploded diagram.
If you have these to sell from a parts-mule later model standard 50 ohm (aka "Std Option 001") 8558B, i.e., not early models with the coarse-toothed knob grip or the Option 002 75 ohm input, and can ship to the UK, please message me.