Sorry tripleZ,
I should have taken into consideration your requirement for 24" or more length on the roller. Here is a link to that concept. These are 3" dia. - .25" thick roller covers.
http://www.unist.com/ASSETS/PDF/Uni-Roller%20Brochure.pdf#page=12
tripleZ,
Here is a link to a product that I have used. It is a complete outfit but you may be able to find parts that will help you in your project. Or, if you are willing to pay the price the whole unit works very well for applying fluid while virtually eliminating waste...