Passage on a freighter - US coast only?

Greetings, everyone and happy New Year!

New to the forum, although I’ve been reading GCaptain and similar maritime news
sources for over a year now.

I’m not in your profession, but I’m fascinated by all of it, and would love to book
passage on a freighter.

I’m self-employed, which gives me flexibility - up to a point - every day off is unpaid
leave, so I need to keep vacations a bit on the short side.

While perusing the options offered by the more prominent freighter cruise booking
agencies, I noticed they cater to those taking long-duration trips.
I can’t take more than about 5-6 days off from my business - the two+ weeks required
for long voyages is more than I can handle.

That said, I noticed that the trips originating in the US start in New York, and "hop"
along the East Coast - Norfolk, Savannah - in all, an itinerary that would work well
within my time budget (costs aren’t really a factor).

Does anyone know of a way to book passage with a freight line, while skipping
the booking agency which hasn’t returned my enquiries?

Any help is appreciated, and if this is in any way an inappropriate posting
I apologize and feel free to move or delete.