If this was bought new then contact Graco or the shop you bought it from as usually pushchairs have at least a 6 months warranty if you bought this second hand Graco should still be able to help or have a look on eBay as they have a lot of spare parts
I would suggest calling Graco to make sure they made one for it. They will need the model number and possibly serial number located on the seat. You can E-mail them or call them.
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