have not seen a new model wayback seatpost in a long time

[eddief]

This one from Soma/IRD looks suitable for some applications:

https://www.somafabshop.com/shop/product/ird-seatpost-wayback-2418

[pinkshogun]

who remembers these..

https://www.instructables.com/id/SR-Sakae-Ringyo-MTE-100-Adjustable-Seatpost-Cleani/

[Mikej]

Cooks Bro’s