This requires modification, one of these may suit
Customer Pay 15% Deposit On Website Only - #7 by ecomlabs by @ecomlabs
Shipping and Payments Restrictions: CS-Cart add-on by Cart-Power by @cart-power
Deposit/pre-Payment - Item Specific Only! (could be ok for you but I had a bad experience with them and they required I remove the negative review before they would refund me for an add-on that didn’t work for me)