You can set yourproducts as pre-orders in Simple Store to collect payments for products that currently can't be shipped. This is a setting for individual products.
To activate the pre-order option for your product, go to the Store > [Products]. Then edit one of your products for pre-orders. Tick the “Show as pre-order and set shipping date.” option, then set an estimated delivery date below and hit "Save".
Then publish your site, the [BUY NOW] button will be changed to “Pre-order” for that one specific product after you active Pre-order option. Your set estimated delivery date will also be displayed in your product description.