There are some Latvian dances in the repertoire of the Society for International Folk Dancing. Our CD10 (available from here, but online ordering not yet possible) includes music for one of them, Jaunais Sturis. I've put a short sample of that here and the dance notation here.

We've recently produced an archive of loads of stuff, including videos from one of our summer schools when several Latvian dances were taught, but I think it's currently only available as a beta release to Society members. I will check on that.

Depending where you're based and how soon you need the dances we may be able to find someone to teach you some of them.

Of course it's also worth seeing what you can find on YouTube such as this and this.