I've found sources for some nighties but not 17. Their website archive says 7 was the last official but nightlies might exist. Fmg might know what was used as from what I can see last nightlies were for 10, but I haven't checked every month since.

17 I think was November 2012 but can't find in the folder. Below is for a 10 with source.
https://ftp.mozilla.org/pub/mobile/nightly/2011/11/

I'll check for a local copy of 17 Deb later. I'll also look how I built embedlite 28 and 29a to see if/ how I got around SSL, gstreamer etc.