Formula a breastfed baby like ?

Hey y’all

I have a 8 month old baby girl pretty much exclusively breastfed ( only work part time but want to work longer can’t if she is exclusively breastfed) but I and slowly loosing my breastmilk supply. I don’t get that much from pumping my breastmilk and can tell when I feed her that it takes longer. I was hopeful this time around I could have enough in me to do both but not working. I also have tried the tea, the cookies and staying water hydrated. Any formula good to supplement?