To be honest mate unless someone has dumped the rom you will be very lucky to find it!
T-Mobile rarely release the ROMs and generally the Ship ROM will appear along side the updated ROM (probably WM 6.1 Update when it arrives).
You can check here for the ROMs:
Sorry I cant be of more help, been having issues like this since Vario 2.
LG Optimus 4X HD - 10f - Waiting JB
Samsung S Advance - Waiting JB
Nexus S - Died
Torch 9810 - Still going strong.
SE Xperia Arc S - 4.0.2.A.0.42 - Loving it!
BB Bold 9780 - Working for now [BIS #Fail]
iPhone 4 - Returned, just not right.
BB Bold 9900 - Returned, OS7 is a step in the wrong direction.
SGSII - Returned, epileptic light sensor, wifi reception was worse than my oldest dongle.
Moto Defy [T-Mobile] - Sold - v2.51