Finally I got the reply from Zalman tech support for the ZM-GWB3850/3870.
http://www.zalman.com/eng/product/Pr...ad.asp?idx=286
This water block is for the PCI-E version only. If this doesn't fits, others HD3850's blocks will not fits. So the conclusion would be:
HD3850 AGP FULL-COVERED WATER BLOCK DOESN'T EXIST. People can stop hunting now.