Squadron 42 add-on

Sorry, but I have a simple question and havn't been able to find any information on this particular subject.

Can Squadron 42 be purchased as an add-on for other packages besides the "Fly Now" packages?

I ask this because I was interested in the Constellation Andromeda package, but can't find info on getting Squadron 42 for $15 like it is with other "cheaper" packages.