Brian,
I'm getting ready to go on my second liveaboard trip in four weeks.
I travel alone and think that liveaboards are maybe the best way to go. On my first trip, there were 28 divers and I'd guess that about ten were singles. So, you are likely to be able to pair up with others to dive with. And, if your first buddy doesn't work out, you can switch around a bit.
If you're willing to share a room, they don't charge you a single supplement.
Last May, I went on a trip to Bonaire with my son. I think it would have been very difficult to find dive buddies to enable me to dive as much as I wanted.
Another good option for a buddy-less diver is to go with a LDS. I went to Cozumel with a group of about 20 from my LDS and that also worked out great....there were several singles looking for buddies and I was never at a loss for someone to dive with. Again, no single supplement if I was willing to share a room.
Some folks recommend singledivers.com, but I haven't done one of theirs. A draw back with them seems to be that they schedule their trips 'way in advance, so you have to commit fairly early, but that's just an impression I've gotten.
Ron