The location filters in Onalytica allow you to restrict your searches to any country. 

To filter your search results to a particular country, open the filters in the search console, and select the country or countries you want to find influencers from.
You can also exclude certain countries if there's countries you definitely don't want influencers from.

Bear in mind that placing more restrictions on the parameters of your search will limit the number of results, so you may have fewer results if you search for niche topics in a small country.