WYSE D90D7 firmware upgrade

Hello!

i'm trying to upgrade my D90D7 (with 4GB flash size) to version BDB0_7064. (need this version in particular for use with citrix xendesktop.

My problem is that the only image i found on the internet is for D90D7 with 16 GB flash size...

is there anyone who know where i could find a image less than 4GB for wys D90D7? i don't understand that there is no different versions. In Citrix ready when you enter the reference of your thin clients for example, it says to install the version 7064 you donwload it and you can't install it because your flash disk is too small... it's pretty anoying because i can't buy new thin clients for the moments...

So if anyone could help me, maybe with rsp file configuration? 

Thank you a lot and really sorry for my poor english, i'm french :)

have a nice day