I order it online - www.spog.bz
- and it's barged over from Belize City, with free delivery to your home if you meet the minimum order amount. It isn't listed on the website, but they often have Alpo available (16 and 37 lb bags). If you send them a message through the site they can let you know what's currently available.
The prices are quite good, and it's nice to have options other than the usual Pedigree.