It's a bit late now but I contacted a 'local' model shop and they came up with this
http://www.servoshop.co.uk/index.php...1044&area=ACCS
It works a dream, and it should also work if you are into miniature boats using a stripped down servo for motor control and drive, with one of these you should be able to get a really small twin screw model to work.
By the way you will be hard pushed to find cheaper servos than on this site, I got four sub min servos for less than £20, great for getting in tight spaces.