Talk to a custom frame builder , to get them to weld something up HD,
get it Heat treated..

if its sticking out so far..


Brompton uses a pretty long seatpost but they are a 31.9 OD/ 1.25",
not 27,2 and add a 30% thicker wall tube for their extended height version.

.. or you could buy 2, have a machine shop re machine them
to fit one into the other , overlapping internally,
and then weld the joint and machine it back down.
(maybe have them do several it may fatigue bend over time.)

I got a Campag 26.6 OD post and a Kalloy one combined in this manner
so I got to fudge the max height line on the Campag one a little bit,
It was still 1" below the max height, but the stability of the stuff
buried inside the frame was maintained..

light, cheap, strong, pick only 2.