Combo feeding

My 3.5mo is exclusively breastfed. I breastfed with my first for 8 months plus donated for 6 of those. However, this time around I feel like I have way less time and patience to pump after feedings, in order to create a stash for myself in case I'm out without my baby (4yo's swim class, activities, etc.) I was wondering if anyone else has "supplemented" with formula for those times that baby is with someone else, and how did it go. She takes a bottle very easily and goes back on the boob without a problem. She also has a dairy intolerance so I'd have to get a special formula (hopefully it will be covered by our insurance). I would obviously pump when I get home so I don't lose my supply, but it's the pumping constantly that I hate this time around. We have an appointment with her doctor in 2 weeks and I'm going to bring it up then to see what they say.