Many compact tractors (or just earlier models) do not have a shut off valve for the fuel line.
But IF you have a Harbor Freight store (or auto parts store) nearby, most will have fuel line 'Pinch off' pliers.
Provided your fuel line is still flexible, this might be a solution for you. You might also be able to 'add' a small ball valve to shut the fuel off in the future if there is space for it.
Amazing deals on this 3Pc Line Clamp Set at Harbor Freight. Quality tools & low prices.
www.harborfreight.com