Marts, give Louis at Liquid Destination a call re: Maldives. He'll sort you out with a spot on his boat.
For Sri Lanka, give either Jamie from The Perfect Wave or Luke from The Surf Travel Company a call. They've both got Sri Lanka covered really well.
I went to the Maldives with World Surfaris last year solo and with mates the previous year. Both boat trips in the Male atolls. Travelling on a boat is cool by yourself providing you're willing to share a cabin, which wasn't an issue for me because the time you actually spend in the cabin is very limited. The Maldives attracts a pretty laid back crew and the people I was with on the boat were great company. If they aren't surf as much as you can!!! On the first trip we had 3 days in a resort the Hudhanshanfwhatever which was fine too and would be ok as a solo traveller because the surf guides there are fantastic and you'll meet a varied crew.
I was hoping that someone could give me some info about the Maldives. What are the options for someone looking to go alone (none of my mates can come with me)? I was thinking of going in September if I could - are there places that people who are travelling by themselves? Is it possible to maybe grab a spare spot on a boat.
Any help that anyone could give could be great. I also thinking of the east coast of Sri Lanka - i think it might have more variety of waves compared to the west coast.