@Juton
For the VF-19 it would depend on the variant, the FAST packs for the YF-19 is compatible with the VF-19A up to Aisha's VF-19E but isn't compatible with the VF-19F or the 19S( havn't encountered blueprints for fast packs for those two yet).
From what I recall I got it at the Sierra Desert area, just can't remember if I got it from hunter guild quest, shop bought or race won.
As for the VF-22 it's compatible with the YF-21 Fast packs and I think I bought blueprints at a shop(?) in the Desert Area.