Vegetarians: your favorite brand of "sausage"?
None I've had are great, but Field Roast is probably the best (however, they only have one kind of smoked sausage, and not sure if it's the taste you're going for), followed by Tofurky. Veggie sausages aren't fatty, so I would brown them slowly with a lot of oil. Tofurky has kielbasa and beer brats, but not sure either really has the taste you're looking for either -- I would try the kielbasa first.
Keep in mind that the veggie sausage won't flavor the soup, so if you want a smokey taste in the soup itself, try adding some liquid smoke. Looks like you're in LA; if you can make it to the SGV, you can get it, no problem.
You can sort of replicate chorizo easily. Whilst you make your soup, in a small separate pan heat some olive oil, add some chopped garlic and just as it's about to brown add a good spoonful of Spanish paprika (preferably the smoked kind or a mix of smoked and non smoked as the taste can be too pronounced). Don't let the paprika scorch and pour the flavoured oil directly onto the pea soup. Beats the addition of quorn sausages in my opinion.