This one comes to mind. It was quite expensive and Uma Thurman's father was involved when I used to get the catalogs 20 years ago. They have private and custom tours available. www.nomadicexpeditions.com

Some others. www.nomadicexpeditions.com www.geoex.com - Digging the 22 day train trip through the Silk Road for $50k

How about around the work via private jet? https://www.smithsonianjourneys.org/tours/around-world-priva...

Ugh. We threw away a ton of stuff. I'll see what I can find. (A change-of-address had lapsed. We let the recipient's family know and they're keeping it updated now, so the torrent has, sadly, stopped.)