I have all my welding and fabricating done by a local steel company. It's best to speak to someone who knows what you want and how to do it! It may be more expensive than off the shelf but at least you get what you want. Draw a picture with measurements and pop in and ask they can only say NO!! If they do B&Q do a nice range of chromed shampoo holders...
Seriously; pick up yellow pages and try steel fabrications they're normally very reasonable but remember S/steel welding requires kit time & skill!
Remember the depth of H2O can go down as well as up.................