The pumps are available - but a period correct knob may be hard to source.
The TR4s (so far as I know) all had pumps, though the knobs matched other TR4 (and Spit) knobs and would not suit a TR3. The knob on my TR4 looks to have been made by a different manufacturer than the other knobs. Most of the knobs (and some other plastic bits) on the TR4 are actually clear plastic covered with a black coating that wears off. The washer knob is solid black - almost like a very hard rubber.