At least in the US Keystone does allow shipping to PO Boxes:



If you are paying by credit card you will probably have to have the PO box listed as a shipping possibility.
And they are still at Amazon ($10 more) but you can have it shipped to an Amazon locker if there is one that you can get to.

Also, they use opennode.com for BTC payments and Coinbase Commerce for altcoins and also BTC.


-Dave