You can replace the Wicked Kitchen Garlic & Herb Nooch Seasoning with 2 tsp nutritional yeast, 1/2 tsp poultry seasoning, and 1/2 teaspoon garlic powder.
For the plant-based puff pastry: In the UK, Jus-Roll sells a 320 g (11.25 oz) sheet of pastry made with vegetable oils. In the US, Pepperidge Farm sells 2 similar sheets of pastry at 17.3 oz (490 g). Use 1 of the Pepperidge Farm sheets, which will be slightly smaller than the single sheet of Jus-Roll. In that case, just use a little less potato filling.