Sticker????
I don't like to make assumptions, because if I knew the game it would be easier.

If you are taking about the panel itself, and not speaker grills, these were molded into the panel at the factory for all late model Williams games starting around 1996 and chrome ink printed.
If you are skilled with silver chrome paint you can mask and spray.

Alternatively, you can sometimes buy a replacement panel either as a NOS or leftover.

If you referring to speakers (earlier games)...

Do you mean a reverse stencil?
They were factory painted as well.

The easiest way to restore the design is with a Testors red enamel paint pen and a steady hand.

If you want to be OCD, you can still find a few extras lying around, buy an old speaker panel, or create you one stencil with a pattern tracer, cut out with an exacto knife, take out the grill, and respray.

Any sticker you make from plastic laminate will look tacky.

Sounds like your best option to "make it look like a Williams" is a NOS panel.

I would post in the MMR thread for help.
I don't know what Chicago Gaming Company or Stern is offering.
MMR is an authorized licensed product, but not a Williams game.
They removed the logo for specific copyright and manufacturing reasons on multiple locations all over the game, backglass, cabinet, speaker panel, playfield, plastics, toys, etc.

It is not going to raise the value any, if you decide to sell the game at some point, it might even reduce the value as it was modified from its original factory condition.
It is like putting an Harley Davidson logo on an Indian motorcycle, and calling it a Harley Davidson.

Owners probably made them out of mirrored plastic, tracing an original from another late model WMS game or swapping panels.
I guess if it makes an owner feel better to "own" a Williams game, great, but an MMR is not a MM in significant ways.

dont stop there, add that Williams logo back on the side cab art.

I think that's the exact problem. You can MAKE one for your own use but you can't SELL one unless you have a deal with PPS (or you ARE PPS).

Mind you, you could always get a Motorola logo sticker and turn it upside down.........

Enjoy (low resolution version).
This is close, but uses raised chrome beveling.

Williams_Pinball_Logo.jpg