I'd try martinus.sk
It's a Slovak bookstore, they seem to be able to source it from the publisher:
https://www.martinus.sk/?uItem=212404
and there is an option to choose 'USA' as a destination country (in the past I placed orders with shipping to Poland and it worked fine). They do accept PayPal.
Please note, that the shipping costs given in the form will not be applicable for foreign orders - customer service will contact you on that once the book is in their warehouse. Possibly worth buying more than one book (they have a good choice of Czech and Slovak books) to save on the shipping costs, as I'm sure these will be quite high.
Michal