28 years old guy looking for room in Vienna

Ok this is a little bit tricky but let me try to describe it :
My name is ceenau :). I am going to be in Vienna for an M.Sc. starting September 2015. So I am looking for a place to rent from September on for a semester first and extend it if it will suite me. BUT I need a confirmation of accommodation NOW so I can apply for the Visa (as a non-EU student) on time. So how tricky is this?
I have applied to a few student dormitories but unfortunately they are fully booked.
I see most of rooms advertised here are to be rent out now but I won't be in Vienna till September.
If you are looking for a flatemate ( GENTLEMAN :) ) from September/October onwards then I'm here but please take into account that I need some sort of proof of lodging in there NOW before I can obtain a Visa and join you :| .
So I'm willing to pay a deposit if you willing to send me some proof of lodging (e.g. lease contract, tenancy agreement, letter of confirmation & residence registration of the person I will live with, ownership papers, etc.).
So please let me know ( private message me here) and we will discuss it further.
See you soon in Vienna