I have a HVAC duct that is almost totally blocked. It has
been this way since my home was constructed. I suspect a crimped vent
or trash in the vent. The problem is the obstruction appears to be a
good distance away from either end. I have easy access from the
basement and from the second floor outlet. In between those is a long
run with several 90º elbows.

I don't want to start tearing up floors and walls to correct
the problem. I am looking or suggestions. I was thinking of a camera
that could be snaked through the vent. Since I don't know which way
some of the turns may be just snaking a standard snake would not
likely be really helpful

Suggestions? Sources for a rent a camera?