SeaLux offer many type of flush mount cup holders which is designed for flush mounting (usually on the gunnel of a boat). This type of Flush Mount  cup holder features a stepped design , which makes it good for holding standard 12 oz. to 30 oz. beverage containers, or larger cups or cans with Koozies. The bottom has a pad lining to cushion cups or cans. A 3/8" tube at the bottom provides drainage. 

SeaLux Marine offer Stainless Steel Cup Holders, Plastic Cup Holders, Color Printed Cup Holders, Water proof LED Drink Holders.