First of all, welcome to the forums!
And congratulations for getting even as far as you did with converting the levels yourself! Unfortunately namida hasn't released a separate music pack for LPOmegaII and extracting music files from old-style nxp packs is rather hard.
So I can give you only one good news: namida is working on an official update of his packs to NeoLemmix V12, which will contain the music files you are missing right now.