I got 3.5" x 2.5", 13" long from Amazon. I haven't connected the light and not sure I will. Got some black vinyl and gonna cover the lens for now. There's another diffuser without the light that I have my eye on but haven't decided if I'm gonna get it yet.
Using the instructions on this thread I changed my steering wheel. It’s a very easy process as long as you take your time and use the proper tools. Thanks For the detailed instructions.