toddler (only child)

hello Moms out there, im currently seeking for tips and advice.. (i have a 3 year old)everytime we go to stores, wether me alone or my husband and i she does a MAJOR tandrum for toys ... its been multiple times already and we have the talk at home or before entering the store..... and it doesnt work i dont know what else to do? i do blame myself and my husband for getting her in the habit of buying her a toy all the time when she was younger... ☹️