Supplementing with cow's milk before a year (just a few oz)

We've been breastfeeding so far, started solids at 6 months, and he's certainly eating plenty now at 9 months. His iron levels were good at good 9 month appt.

I'm considering supplementing with a small amount of whole organic cow's milk. My pumping during work has been less and less productive and my freezer stash is almost gone. I have a work trip coming up in a few months I need to do something so I can build it up enough to be away for a few days. I don't want to give formula as I can find a single one that doesn't include at least one ingredient I wouldn't eat myself.

Anyone else given cow's milk before 1, how did it go?