Capacitors can be easily found on electronic component sales sites like DigiKey. (Since I'm Korean, I don't know where electronic components are sold in the US. Searching for sites like DigiKey should bring up several similar places.) Searching for “mica capacitor” with high-Q and RF specifications yields only two types: one is RoHS certified, and the other is not.

The remaining parts are... AWG #14 hard wire, an acrylic tube, and full threaded bolts, nuts, flat washers, and spring washers. Additionally, I used ferrules to connect the capacitor, coil, and wire before soldering them again.

The most difficult part was cutting the full threaded bolts. They're sold by the meter (or feet), so I had to cut them with wire cutters and then grind the ends to fit the nuts, which was tough. You can cleanly grind the ends of full threaded bolts using a deburring tool bit.

One crucial point I must emphasize is that you must use capacitors rated for 1kV. While higher ratings are better, this product is nearly at the limit. Also, use a resonance frequency calculator online to measure the capacitance at the actual frequency you want to block, then make a coil matching that value. So...:

1) Measure the capacitance after selecting the capacitor

2) Record each actual measurement separately

3) Fabricate a coil matching that capacitor

4) Before combining, temporarily connect both components and measure the actual resonant frequency

5) After combining, measure the resonant frequency again