Large quantities were produced during the war and there was a later aluminium version which, of course, was a lot lighter. Whilst some of this useful material is still retained by the military, large amounts became 'Army Surplus'. Calumet Industries in the USA offered PSP when I first published this post but they seem to have disappeared. But etp-trade.de have information here (including installation instructions in English and Russian!).
I've spotted 'PSP' finding a secondary use in a number of places, particularly in the far East. The most common use is for fencing, where 'PSP' can form the horizontal rails joining brick pillars, like the example below from a private house in Yangon, Myanmar.

Yangon (2013).
The boundary fence at Thandwe Airport in Myanmar seems to be entirely made from 'PSP' horizontal rails fastened to concrete posts, as below.

Perhaps the oddest use I've spotted was during a visit to Sittwe, in Myanmar. I visited a former Merchant's House (described in the section 'Merchant's House' of my post Sittwe, Myanmar) where 'PSP', enamel painted white, is used to panel-in the staircase.

Air conditioned-cladding for the staircase in the Merchant's House.
There are more pictures of the Merchant's House here.
I'm confident that there must be more outlandish uses for 'PSP' out there - I just haven't noticed them. Can anybody help?
[Dead link to Calumet Industries updated 10-Jul-2019]