Where can we purchase new 24' pine beams? We would prefer not to splice.

You don't need to, I routinely build with full length plates and ties

Long sticks are not hard to find, 24's can be had right here in town, there are two mills within an hour of me that will saw to 30 and 40'

I suspect there are sources closer to you I am not aware of.

There is a timber broker in the state most area framers work with, I'm certain he will be able to arrange puchase through a closer source and provide delivery. I'll e-mail his contact info