I mix mine up with low sodium soy sauce, ginger, garlic, chili-garlic (sriracha), and sometimes add no-salt no-sugar natural peanut butter and agave nectar. I also go to Asian markets to buy hoisin, fish sauce, nuoc cham, etc, but those can be high in sodium.
If you want to buy a sauce prepared, there are some places that carry no-sodium products like Mr. Spice
Have you tried any other ways of preparing your veggies? My favorite is just oven roasting fresh veggies with a little olive oil, sea salt, and fresh cracked pepper.
Frozen veggies aren't nearly as palatable to me, and sauces are good for covering that up. Maybe fresh veggies would give you more opportunity for variety.