Hello Szymon!
First welcome here! Have a nice time here!

What kind of maps you are looking for? Digital and online maps, or oldfashioned maps of paper?
I know some sites on the www, where are marked cyclingtrips, for example gpsies.com (some different languages possible), also our Radreise-Wiki has some sites listed, there is also a list of mapshops in it.
Perhaps you tell us more about what you´re searching!
Greetings