I have a 2017 F150 Lariat that I will have a Line-Ex spray on bedliner applied to early next week. The truck came with the drop in bedliner with the liner on the tailgate. I removed the bedliner and the tailgate liner but the screws used to secure the bedliner through the access cover have a large "stand-off" washer that I can't remove from the Torx screw. I was going to order from the local dealer but he doesn't have them in stock and won't get more until Tuesday which is the day the Line-Ex is supposed to go on.

My question is: Since these are steel screws, can I source them locally at a hardware store? The head of the screw will be contacting the aluminum access panel so do I need to use a fiber or nylon washer to avoid galvanic corrosion? It looks like the screw goes into the internal tailgate frame that has steel inserts.