Hello,
I am a degree qualified Product Designer. I have experience in designing new products and modifying existing ones.
In regards to this idea I will design the new cover for the paint roller, draw it up in SolidWorks CAD for you, provide you with the files along with a 3D Printable version should you wish to mock it up.
To finish off you will be provided with a technical drawing detailing the sizes of the case. Along with this I can provide you with some renders of the finished product.
I can have this turned around within 2 days for you.
Kindest regards,
Thomas Wright.