Having seen the real buttons up close, I knew exactly what I was looking for, but I had no idea where to find them. I started going to a bunch of stores that I thought might carry this type of item. Lots of stores had similar buttons, but nothing that was the right size. I went to Home Depot, Lowes, Michaels, Target, and a few others.
Next, I did some searches on the internet, using what little information I knew about the real buttons. After a few searches and turning over a few rocks, I found a couple of items that came really close to meeting the criteria I had defined.
I ordered a few different types of buttons from a couple of different vendors, and sure enough, one of them turned out to be dead on.
I'm very happy to have found these pieces, as they can easily be used to create a multitude of Enterprise props. These buttons are used on the padds, wall coms, desktop coms, and pretty much any other type of control panel on the ship.
The only difference between these buttons and the ones used on the show are that these don't have numbers silk screened on them. The ones used in the show have three digit numbers on them. The white buttons have black writing and the grey/black buttons have white writing.
The buttons can be found online by doing a search for "3M rubber bumpons". Click here to download a spec sheet on the product line. If I recall correctly, the correct ones are the ones seen in figure 1. SJ-5008 SP 3M Rubber bumpons. You'll need to find a place to order them from, as most retail stores don't carry them. They use grey, white, and black on the show.
For the lettering, I have found some chartpak letters that are useful. They are not perfect matches, but they look very nice. I use Chartpak Velvet Touch Lettering, Helvetica 10 Pt. M5210N. You can try looking for this stuff at Drafting Supply houses, high end art supply houses, or online.
The letters do not stick very well to the buttons, so you will need to spray on a coat or two of clear coat once the numbers are in place to keep them on.