Believe it or not, there are several companies out there that have started to reproduce a lot of the hard to find items. With things like artwork there will only be a short run every few years for some of the more rare titles, but the more popular games have reproduction parts available from many vendors.
There's a company that has actually reproduced the yoke for the Star Wars games and they are also looking into having the vector tubes reproduced for the old X-Y games. So the rare stuff is getting easier to find in some cases. It'll be expensive, but at least it's available.
I picked up a Dragon's Lair cabinet a couple of weeks ago that has been converted to some generic 1990's era game. The area where the marquee mounted had been cut to allow a generic marquee to be installed. I can buy the replacement wood panels, marquee brackets, marquee plexi, and the repro marquee itself to restore the cabinet back to its original shape. So a few months of work and a few hundred dollars in parts will get this classic back into working shape.
Videotopia is a museum display that travels. They currently have a setup in Tallahassee, Florida. I saw it last Friday while passing through there. They have everything from the first commercial video game (Computer Space) through some late 1990's era games.
There are more working classic video games today than there were ten years ago. It's not cost effective to refurbish and keep them running commercially, but there are hundreds of home arcades where people collect, restore, and share their games with their friends. I have a home arcade with 60 video games and 5 pinball machines. My collection is small compared to many of the others. So the arcades and games are not gone, just no longer in public.
Do a search online and you may be able to find someone locally with a nice arcade in their home that has an occasional game night open to everyone.
A list is only as strong as its weakest link. -- Don Knuth