Too late like you’d already used some of it (shampoo for example?)
After you have gone to confession about stealing, and done your penance, send (anonymously) the money that the product would have cost to the store, print a note that you took a bottle of shampoo (or whatever) without paying and here is the money you should have spent. No need to sign your name. And then do as Jesus said, “Go, and sin no more”. God’s love and peace be with you. We all make mistakes. . .but by the grace of God we don’t have to always keep making the same ones.