A Cane Creek Thudbuster ST, but only 27.2 or larger ..
Smaller ID seat tubes would get the USE, seatpost, a 25.0 telescopic type.
they machine shims to 27.2, then also offer a 27.2 version , as well,
and shims to fit larger seat tubes.

Both these can be refitted with different rate of suspension dependant on rider weight.

there are cheaper seat posts as well. they often have rotational play in the telescopic
mechanism, but are widely available .. if cheaper is priority..

I have an Airwings , a German made suspension seat post as part of an OEM,
My Koga, WTR Build,
but those may need be imported retail from EU.

Have a thudbuster LT on my Bike Friday, but it needs a long seat post extension
like sloping top tube frames may offer,
as the parallelogram linkage uses up 6 inches .
that too has multiple elastomers of various rates for the backside on the saddle.