This is par for the course unfortunately. I am not sure of the best way. I usually get ahold of them at some point through PM. Maybe email or call them and leave voicemails until they get back to you.
In the future I would advise you to order their parts through TheZStore.com. That way they are the middle men and can refund you if it takes an excessive amount of time if it is not in stock.
Good luck
