Top part is usually aluminum. Calhoun's in MN has a different shim in their telescoping seat post ,
steel main section, upper is 27.2 so you can use a nice integrated saddle clamp type,
though they will include a budget one.. Kalloy for either , I expect. http://www.calhouncycle.com/productc...&idproduct=873
another shim with an ID of 1" would let one use a chromoly plain seatpost
such as sold under Red Line brand..
Might still be some Ti main section posts, around..
QSPTTOP is aluminum ,QSPTS , the larger bottom tube, is steel [or titanium]
with the rubber Bung in the bottom and a plug in the open upper end
of the 2 seat post parts.
a modest bit of cleverness , you can fix a piece of cable inside the seat post
anchored in the end of each.
Of course you can always just fold the bike up and bring it inside.
I think the 2011 X code light weight Brommy versions have the QSPT
A,for aluminum now
rather than Ti ... spotty sourcing, I hear.
But I don't own one. so Im not sure .
another clever option : a flat-washer that is smaller than the ID of the tube ,
but larger than the ID of the bushing at the top of the tube ,
and having that fixed in the bottom of the upper section of the combination.
will stop it from pulling out.