Supplementing with formula only when not with baby

My 6 mo old is EBF. I have a decent freezer stash however when I am away from him he eats anywhere from 40-47 oz in 24 hours. I’m a SAHM so this isn’t a problem daily however if my husband and I want to go on a weekend trip, I do not have enough milk for him. I’m wondering if anyone supplements with formula only when away from baby on occasion or if that is even an option ? Can I expect gas or stomach upset from occasional use of formula if he isn’t getting it everyday? I would pump while away to maintain my supply, more worried about how it may affect baby.