Insert binary file into bytea where PG server does not have access to the file ?

11.5 on linux

Big corp with an IT dept providing us with PG DBs running in instances on
their servers. (We/I amd not DBA). We on the client side, the "users" of
these DBs, want to load binary files into bytea type columns. But the
files we want to load are on disks that the server does not have access
to.

I googled around for a solution. This failed...

insert into test_bytea (id,data) values
(1,pg_read_binary_file('/top/next.whatever/xyz.bin')::bytea);

ERROR: could not stat file "/top/next.whatever/xyz.bin": No such file or
directory

Understandable because the server hasn't even mounted /top.

Is there a way to do what I want from the client side ?
If the file is transformed into some titanic string on the client side,
then passed along over the net to the server in the insert statement, is
there a max string length that I need to worry about ?

Thanks