Can't find The PVA Company on ebay, found their web site which is still under construction.
Found some of the stone carp bags on the bay, but nothing else?
Not wishing to tell you how to suck eggs - make sure it is wetted thoroughly before tightening.
Palomar knot is good and easy to tie, I've been using it a lot more lately.
But do test it.
Pound shop, most supermarkets, expensive ones, cheap ones, ESP, others I can't remember all go after a short while.
The best one's I've had so far were short and stumpy and cost £1.00 of the tackle shop counter; not sure which make if any.