So there seems to be two options:

(1) Ask the British manufacturer to provide a statement of compliance.
If this is simply a letter they provide, then I can probably get that.
If it requires them to do a bunch of paper work, file this all with
the DOT, an so on, then it's likely the shop that made the trailer for
me will want to take a pass. Does anyone know off hand what's involved
for he manufacturer to provide a statement of compliance? If not, I
imagine I'll get to spend some quality time on the phone with the DOT
(which is looking likely anyway).

(2) The container option sounds interesting. Would this be as simple
as declaring that it is a container, that it will not be used for road
transport, simply storage, and then haul it away from the port on a
flatbed? If so, then that sounds like it could be the way to go.

Thanks in advance for all of the assistance.

Chris