Check
this and
this out.
Currently, I have FINALLY found my e-Reader and I want to find my other GBA to test these out for real... >_>
Basically, no, there is no AR codes, but you can use hacked save files compatable with the EUR 1.1 VERSION of the rom. It took me a while to figure that out, since there is no proper documentation...
Basically, use the hacked save files from the Youtube page, and run the game in No$Gba with E-Reader code support to add other Powerups and stuff.
You can use the other resource site to add them to your legit cart if you have one. Those e-Reader .raw files are good for any version of the Rom (note, EUR rom does not natively have e-Reader function enabled it is hacked in in the save files with e-Reader levels).
Those levels are really fun.
A lot of unique things in them.