Source for ceramic disc and silver mica capacitors

Buying ceramic disc and silver mica capacitors.
as used in several frequency conversion articles, and an explanation of their temperature coefficient.

Radio Shack Online skip to pages 6 and 7 for smaller value ceramic discs.
RF Parts Co. fairly good supply of silver micas like used in receivers and 220 exciter conversion.

What does the NP0, N750, N1000 all that stuff mean?

NP0, (N-P-ZERO) A capacitor with the designation NP0 indicates this capacitor is basically very value stable over a wide temperature range. This range is usually -25° to +85° C. NP0 stands for Negative Positive Zero. The amount the capacitor actually changes value is something like 0+ /- 60 ppm / degrees C. This designation is very often misidentified as NPO (N-P-OH). NP0's are commonly used in tuned RF circuits, as are silvered micas.

N750 and N1000 are similar to NP0 as they are often used in frequency stable circuitry. These types are not as stable as NP0 types, however are cheaper to produce.