Dog Food SAMPLE Beef / sensitive (Sheldon)

Hi, I'm looking for BEEF flavour or Royal Canin dog food if anyone has any ideally dry. She can't have fish it seems. Or anything with too much poultry in. I'm only looking for a small amount or sample. The reason being my new dog has a sensitive stomach and skin, I'm trialing foods she's ok with, which is proving a little expensive. So looking to sample small amounts to see if it upsets her tummy or not before spending £40/£50 on a pack which then goes to my other half when it doesn't suit the doggo.