Go to your My eBay > click the ACCOUNT tab >   select SITE PREFERENCES >  BUYER REQUIREMENTS, click "show" & then EDIT

Select - Bidders who have a primary postage address in a location I don't post to

BUT you must select countries you do not post to while listing

While you are doing the requirements you may as well tick everything to block bidders who:

-Have received 2 Unpaid Item strike(s) within 12 Month(s).

-Have 4 Policy Violation report(s) within 6 Month(s).

-Have a feedback score of -1 or lower.

-Haven't gone through phone verification. - Only apply this block to buyers who have a feedback score of 5 or lower.