Yep, tomatoes in general will need about a 5 gallon pot (18" across), while peppers seem to do fine in a 3 gallon pot (14" across), although neither would object to having more space to wriggle its toes!
You could plant a tomato in a pot and add a tomato cage, then put a few pea plants in front of the tomato. I'm thinking that the tomato wouldn't really take off, size wise, until the peas were done... and the peas could climb the tomato cage. I've planted cucumber seedlings in front of pea plants, same idea, both use the same supports with the cukes taking over about the time the pea vines die back.