Both Brazilian Penneywort and Anacharis are stem plants, and there are numerous to choose from. If lighting is your concern, avoid any of the 'red' varieties as they require more light. I've only tried a few stem plants. Brazilian Penneywort, Wisteria, and Bacopa Carolina. Of the three, Wisteria is my favorite even though I know several others have not had good luck with it. I got mine in PetSmart, it came in a tube. The ones they sell are grown emersed, so they'll eventually loose the leaves they have and new growth will look completely different once submerged. Don't expect much in the first couple weeks...
Have you tried looking at the profiles here? Blue bar at the top, second link. Mostly fish in there, but there is a section for plants too. Tropical Fish Profiles
If you just want some 'easy' plants, look at Java Fern and Anubias. They are two of the easiest, and are pretty slow growers.
As for ordering online, you can try ebay (I hear people talk about mikeswetpets is a good seller), aquabid, or websites like liveaquaria, aquariumplants, or plantedaquariumscentral.
For QT just keep them submersed, with light and heat for a week. Heat generally speeds up the life cycle of nasties, so warmer water makes that happen faster.