I’m intl a lot and Starbucks is usually the easiest way to guarantee finding cold brew (most non-US countries super far behind here). Almost every country has at least one unless sanctioned, super small or super undeveloped. 

In Riga I remembered this place from last year though with excellent cold brew https://maps.app.goo.gl/dMzZLxkL7GLYiHaP6?g_st=ic