^ This. I did some bootstrap work for a client which almost went as far as to have a mini mock ecommerce store which just displayed 0 stock, but you could clic

^ This. I did some bootstrap work for a client which almost went as far as to have a mini mock ecommerce store which just displayed 0 stock, but you could click the giant button to get a reminder when it's back in stock. Quick and easy idea validation, and if it's validated, you have a nice list of targeted users.