Is it OK to purchase cat food?
I also understand that eating meat (something I admittedly still do
  myself) is frowned upon


It depends on the tradition and personal beliefs. If you follow Theravada Buddhism, you wouldn't have any issue with feeding yourself or your cat with meat products. In Theravada Buddhism, the word of the Buddha is valued higher than personal opinions. So you or your cat is less likely to get frowned upon, just for eating meat. :) Vegetarianism is usually treated as a personal food preference.