These things have GOT to exist in the USA, but clearly the name is
different.

They are used with metal conduit-and-box wiring systems, wherever you
want to bring a flexible cable out through the wall of a conduit box
with better waterproofing than a plain grommet.

Not quite the same, but perhaps usable are the split gromets. See
MSC's on line catalog http://www.mscdirect.com at page 3643, or search
for "split cable entry system" using their site search engine.

Or, you could use a standard cable entry boot from Andrew
http://216.91.65.4/pdfs/andrew/221213.pdf

Jack K8ZOA