If you don't want to go full-vegan, whey protein isn't bad. But you shouldn't rely on any one source exclusively.

Full-vegan options include quinoa, beans, lentils, and nuts. But I agree it's hard. You have to eat a lot of these things.

I don't use any protein supplements but I've heard good things about Vega's products http://myvega.com/

+1 to Vega, for sure.

You can also get hemp-based protein as well.

Nuts and beans are both high in protein; quinoa is a complete protein (as is soy) by itself.

I get most of my protein from tofu, honestly. It isn't as protein-dense as beef, though.

This isn't a problem with plant-based protein sources, its a problem with commercially-processed packaged foods. You can get high-protein non-meat protein sources that aren't as heavily processed (e.g., gluten powder, tofu, quinoa, etc.) and prepare them yourself to control sodium levels.

Don't eat veggie burgers then. Eat beans, nuts, tofu, seitan, flax - all of them are low in sodium.