These capacitors need to withstand atleast 400V as far as i can tell, so chose 600V or better 1000V (highly recommended). I desoldered C18 on my ADP-160ER and measured it 56pF (size is 1206, most types are C0G/NP0, but X7R would be enough). Some manufacturer part numbers from a quick search: GCM31A5C3A560FX01D CC1206JKNPOCBN560 C1206C560JDGAC7800 C1206X560JDGAC7800 GRM31A5C3A560JW01D CHV1206N1K0560JCT. You are probably good with 30pF to 70pF if thats better available.