Hi! If you're looking for something squirrel-specific, you probably want one of the rat blocks that are made as sole diet for lab rats. Harlan Teklad (not sure of the exact name) is used by some people here. You have to order it online.
I use Mazuri Rat and Mouse Diet. It's probably cheapest and easiest to buy if you have a feed store anywhere near you. It's gone up to $23.00 a 25# bag for me now and probably going higher. My crew has had very little during these times of plenty. Most of them aren't looking for anything from me, so I just put a handful out for the few who still do. I feed much more in winter, when many more come looking for it.
What is your situation? $300 a month?!
How many little pigs are you feeding? Do you feed every day? Are you feeding with other critters in mind, or just squirrels?
If you do find and switch to one of the rodent blocks, your crew may not be very appreciative at first, but especially come winter they will see the benefit of easy, quickly obtained nutrition. Mine do anyway.