The Chicago Tribune has a piece on how solo travelers can buy vacation packages without getting fleeced by the single supplement. I've written about these points before but they always bear repeating.
If you're willing to share a room, many tour operators will match you with someone of the same sex, eliminating the single supplement. Some will waive it, even if you end up with a private room due to an odd number of men or women on the trip. Don't get your heart set on it. You have to be lucky for circumstances to work out that way.
Booking early or late can help, as can going with smaller tour operators willing to negotiate.
The Tribune story says the single supplement is typically 200 percent. I don't believe that. On cruises, maybe. But I've been on a lot of vacation tours (biking, rafting, horseback riding and more) and perused many a travel catalog. I've never seen the single supplement listed as 200 percent.
Instead, you usually end up having to pay several hundred dollars more than those who bunk with another, whether friend, partner or spouse. That's because the hotels charge by the room and if you're just one person, you can't split it with anyone. But that's not the tour operator's fault. It's the way of hotel pricing. The tour operator books a certain number of rooms and if two people are sharing a room, the overall costs are lower.
Over the years I've experienced most of the above. I've shared rooms with someone the tour company matched me with. I've gotten my own room because I was the "odd man out" among the women on the trip - the lucky one who asked for a share but got a single. I had a single when I was on a rafting trip because the sleeping quarters were tents. Which is not necessarily standard. On a camping and biking trip, I was assigned a tentmate.
I've rotated roommates on a trip where there were three solo female travelers. I thought that was a good, fair system, rather than giving the single room to one person for the entire trip. The only problem was, I got so friendly with the other two solo female travelers I felt lonely on the nights I got the private room! There they were chatting and laughing without me!
Anyway, don't let a single supplement put you off taking a vacation package with a tour operator. Choose one of the above options. Or, if you choose a private room, calculate if there are savings based on group travel and transportation that the tour is providing that you wouldn't have gotten on your own.
If you can't bear the idea of sharing with a stranger or paying a single supplement, I'm out of ideas for group trips for you. But if you're willing to try the roommate route, just remember that you won't be spending a lot of time in your room anyway, particularly on an adventure trip...the kind I like to promote here.