Hello James, since it was once something I personally got into, I can tell you that there is a very wide variety of things that can increase muscle production, and quite fast.
You can begin by introducing more protean into your diet, as a vegetarian, I did tofu, soy protein and nuts. Protein is essential in maintaining amino acid chemical buildup, and therefore can boost your results drastically. Likewise, lack of protein will shrink muscle mass, and make you frail.
You can also eat meat, protein bars, protein shakes, use "bulk-up", whey protein, and much much more.
I would not buy anything on this matter off the internet, because that would be a waste of your money. Just do some research, usually 99% of the world concurs: protein and excessive= massive results
Cheers, Ferdinand