A while ago, I put an Eject Button in the VW. At the time, I put an external port in the garage remote, and it totally paid off: I just transplanted it.
The External Port
To put the port in, I got a mono audio cable from Amazon & cut it. I soldered the panel-mount jack to the inside of the garage remote and connected the plug to the eject button. It came out looking reasonably good on the remote.
I thought I may have been wasting my time back then, but it made it easier to move the opener to a new car without desoldering anything.
The New Button
Sadly, I could not find a custom-engraved OEM button that said "Eject" to go in the new car.
But I did find a switch cover just like what's already in the unused button spaces. I drilled a hole in that and glued in a momentary switch and pigtail connector. I soldered the pigtail connection to the mono audio cable. A little heat shrink tubing kept things nice & neat. Now pressing the button activates the garage remote.
The switch popped right into the unused button space on the lower dash.
I didn't hook up the 12V power, but I might do that later. That would make the ring light come on, which would be a nice touch.
I routed the wires through the dash and hid the opener inside a trim panel. It came out looking pretty good! Having a port in the opener was nice: When I sold the old car, I pulled the opener out and hooked it into the new car. Having a plug at the end (instead of a whole remote soldered there) makes it much easier to fish it through the dash. All of the soldering was done at a workbench, instead of kneeling next to the car. For once I wasn't over-complicating things: I actually used the portability feature I built into the remote!