Hello everyone,
i’ve just found these two hd44780 compliant displays at amazon:
20x4 white letters on blue background - 6.69 € - http://www.amazon.de/Display-Anzeigen-Zeichen-kompatibel-HD44780/dp/B00ALNHTVY/ref=cm_cr_pr_product_top
16x2 white letters on blue background - 3.29 € - http://www.amazon.de/HD44780-Module-Display-Anzeigen-Zeichen/dp/B009GEPZRE/ref=pd_sim_ce_1