Non Refund of Advance Booking Amount/Margin Money

Sir, We are supplier and trader of Stainless Steel Food Vending Carts and supply Food Carts to vendors. Normally we follow the procedure of taking 10 % of total price of the food cart as booking amount as it is a customised product which is manufactured as per order and takes at least one month time to manufacture the cart from the date of order. Off lately we have encountered few buyers coming up for cancellation after 15-20 days of booking citing the excuses like need money for medical issues in their home, not interested now, will buy later or changing of their minds and many illogical reasons. After contacting the manufacturer we received a reply that they cannot refund the money as they have bought all the raw materials for making the cart and are on the verge of completion. Since it is a made to order product no one buy the product soon and they will have to bear the liability till its sold. So how can we write any clause in our money receipt so that we can not only protect the interest of the manufacturer but also save the buyer from being afraid of depositing the booking amount which they might not deposit if they fear of losing it completely as they are urban poor people.