Oddly enough, koalas crop up in a ukulele video in Croatian, by Karkanjerac :
No luck in my search for a Slovakian ukulele player yet, but I did however find a video that was filmed in Slovakia, though you won’t really be able to tell.
Pvnova and a friend, Erasmus students in Bratislava, are doing a cool ukulele and guitar cover of I like what you say by Nada Surf. The song has been given an international feel, with extra verses in French and German in the end (Their grammar is voluntarily dodgy to fit whith the rhythm).
Update : I have now found a Slovakian ukulele player, playing a traditional tune in this video uploaded just yesterday: