The Scotts "Ortho" VOLCK oil spray concentrate should be available from many ACE Hardware stores, KMart or HD.
ACE Hardware stores with Garden Centers would probably be more likely to stock it.

Anything that says "horticultural oil" is equivalent.

I found it last summer at the Lowes in Albany but they didn't have a huge supply of it. I have also had very good luck with my gardenia using Ivory Liquid and water in a sprayer. A good friend that is an avid gardener recommended this and told me its all she uses on Gardenias, etc. that get that icky black gunk from white flies, etc.

You might also try that new nursey, DIG, that just opened out on 82.