Where could I find the Igros K'naos regarding Rambam's works for free online? In particular I am looking for a quote from Radak about the aggados there. A screenshot of that page would suffice.
As noted by @TamirEvan the Igros K'naos are part of the 1859 Leipzig ed. of Kovetz T'shuvos HaRambam. The quote from Radak can be found on page 3b there.
Text from the 1859 Leipzig edition: http://www.sefaria.org/Iggerot_HaRambam,_Iggeret_Kanaut