Since that's not the most convenient source, look for packaged commercial sources that are organic and not from concentrate, with no additives. (greensmoothiegirl.com)
This is a step which people typically take when they are unable to get loans from commercial sources. (businessinsider.com)
A good commercial source of information is PetAlive Vi - Pro Plus to Naturally Prevent and Treat Distemper in Pets (dog-health-guide.org)