You can buy IK415 by the BKV, but unfortunately it isn't 100% complete:

http://bkv.hu/hu/felajanljuk_megvetelre/autobuszok_131022

But one IK435 is totally complete! :-)

You can find some 280.02 for sale at Hajdú Volán:

http://www.hajduvolan.hu/ikarus-195.html

I'm not sure that every vehicle is still exist, for example the BPY-s are scrapped