A letter/email to customer thanking them for their request but rejecting a product order due to insufficient supply of stocks.
Due to high demand, it will take longer to replenish the stocks and the new stock will be more expensive. They will immediately replenish the stocks, but it will take a certain number of days for the new stock to arrive even if everything goes well. In addition, the unit price for the new stock has slightly increased to [amount] per unit. It seeks confirmation from customer as to whether to proceed with the order in terms of whether they would like to order on this basis (the more expensive stock) or be put on a waiting list until stocks have been replenished.
out of stock,