Senegals get on average to 12", sometimes a big one will push up to 14", but no larger.
I'd agree that you could get away with a 40, but prefer a 55 if it's possible. Then you can get several!!
I've found the price in Canada varies from city to city. On the prairies if you can get them under $20 you're doing ok. Some of our friends from down south might find that's overpriced, but they still aren't all that common around here.