One option would be to put a very low profile switch under the Amiga, so you just have to lift it a little and slide your finger under to flip it.
Another option would be to put the switch at the back where the ports are. It won't be seen.
Of course, all of the above still mean drilling an extra hole in your Amiga (even if the hole is hidden).
What about setting a tiny push type switch into one of the holes on the bottom of that Amiga where there already is a cavity for a screw hole? The A500 case would still hold together fairly well with one screw missing.
I do think a nicely mounted switch can sometimes enhance the look of the Amiga, if done professionally.
