I am not very familiar with this tech, but will research more as time allows. So far, I have this:

Component   Specification   Recommended Part
Adjustable Capacitor (C1)   10 nF – 500 nF, 1500V – 5000V   Jennings CVDD-1000-20, Cornell Dubilier 940C
Adjustable Capacitor (C2)   10 nF – 500 nF, 1500V – 5000V   Jennings CVDD-1000-20, Motor Run Capacitor
Tapped Adjustable Inductor (L1)   5 mH – 200 mH, Air-Core, 10A   Ohmite Z-50, Hammond 1535B
Load Resistor   50Ω, 500W, Non-Inductive   Caddock MP930, Vishay RTO50
Directional Coupler Transformer   1:1 or 1:2, 1 kHz – 50 kHz   Amidon FT-140-77, Bourns 6000 Series

Not sure at this time the winding spec for an air core 5mH - 200mH inductor, but this design is interesting variation of roller type air core inductor: https://pa3fwm.nl/technotes/tn09c.html

Here are some potential hints:

Recommended Coil Dimensions for 5mH to 200mH Air-Core Inductor
To achieve the required inductance range, we will use a large-diameter coil with multi-tapped windings.

Parameter   Minimum Inductance (5 mH)   Maximum Inductance (200 mH)
Coil Diameter   100 mm (4 inches)   150 mm (6 inches)
Coil Length   100 mm (4 inches)   200 mm (8 inches)
Wire Gauge (AWG)   12 AWG (Thicker for 10A Handling)   18 AWG (For Higher Turns & Inductance)
Number of Turns (Estimated)   120 - 150 turns   450 - 600 turns
Spacing Between Turns   1.5 - 2 mm (to prevent voltage breakdown)   Uniform winding with PTFE insulation
Voltage Handling   1000V insulation recommended   1500V+ for maximum ratings

Not sure on the accuracy of this, but thought to share it anyway.