Did you see this thread (above)? It's got a couple of links for sources. Be prepared to experiment a bit, though, because it seems like different people like different supplements. The algae oil (DHA source) has a very fishy taste, so a lot of the supplements cause fishy burps for several hours in some people. I've found that with a lot of them, but over time I've figured out the brand that works best for me, and I've also figured out how to take it time wise. For me, it works best to take it before a meal, preferably before a highly flavored meal (like Thai food or Mexican, but not before a piece of toast!).
We've tried a couple of vegan algae oils for our child when he couldn't swallow capsules yet, and all the ones that we tried were very fishy. We broke a bottle once, and our house smelled like a cannery for a week!
Our son did seem to adapt to the taste, though, and he eventually took it fairly willingly with some fruit juice.
One other note - be sure to check that the capsule is vegetarian as well. I've noticed at least one brand (can't remember which one) which sells a vegan oil inside a gelatin capsule! Obviously if you buy from a veg store then it's not an issue but beware if shopping elsewhere!