A college with a recording studio asked us if we could help with the operation of a particular button on a Mackie Onyx 1620i sound mixer. Users with disabilities were finding the "Talkback" button difficult to press.
We considered electrically connecting a disability friendly switch in parallel, but this proved difficult due to the nature of the circuitry the button operates, and the desire to make any modification reversible if the panel was ever sold on.
Instead, we took a template off the front panel and constructed an easy to press lockable button to sit over the original, and secured by a couple of longer screws in existing panel securing points.   
Construction was a combination of 22mm copper tube, copper plate, and a button machined from an engineering plastic called acetal. 
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Photos of the Mackie Onyx 1620i, and on the left, the button in question and the existing panel securing points we will use to secure the modification.
Below, various photos during construction.  
A dense foam pad was added under the new button to protect the old one and prevent excessive force being applied. A supplementary return spring was also added. This photo shows the simple twist lock action.
Harrogate and Ripon Group