I have heard that the best version of the Bible and New Testament in Slovak is the Roháček version.
Amazon - Slovak New Testament / Pismo Nova zmulva / and Hungarian New Testament in Mirror Translation
This is a Slovak-Hungarian New Testament Bible.
Bible In My Language
BIML is selling many printed Slovak Bibles on their website.
Bible Society - Slovakian Bible
This Slovakian Bible uses the traditional Lutheran translation.
Canadian Bible Society
The CBS has three Slovak Bibles available for sale on their website.
Ethnic Harvest has a page of links where you can read the Slovak Bible.
The Slovak Bible is available on the website of Multi-Language Media.
Slovak Bible Society
You can purchase the Slovak Bible at Slovak Bible Society.
The World Bibles site helps you to find Bibles in over 4,000 languages including Slovak.