Go on over to the ProntoNG forum and files sections and look for posts and pcf files from "LOWPRO." He has done what you want to do in spades.

You will need to download the ProntoNG editor (which you can get off Remote Central or from the Philips Pronto website) so that you can read a pcf file. Note that codes in pcf and icf files are identical, so you could copy Lowpro's IR codes into your icf if you need them.