Wood wanted for making two cupboard shelves (Kinson Village Green Stocks BH10)

Hello. I'd like to make 2 extra shelves in my son's wardrobe, but cheapest I can find for suitable wood is £30+ at B&Q!! I can cut wood to size. Looking for something like pine/solid wood/melanine. Each shelf is 44cm x 40cm so anything I can cut down to fit. Needs to be 1.5-2.5 cm deep. Thanks