i have to start supplementing my baby with formula because I can't keep up with her demand. I have a small stash saved…

i have to start supplementing my baby with formula because I can't keep up with her demand. I have a small stash saved of breastmilk but I am lucky to be able to pump maybe 4 times a day and that's when I am still home and not back at work yet. I am going to be working 25-30 hours a week and going to school Monday- Thursday and I won't be able to pump that much to keep my stash going. is there any formulas any mommies recommend for supplementing? I will still nurse her when I can and pump when I can but I just don't think it will be enough to keep up with her needs.