Need help to get HD caddy part number for Optiplex 960 DT

I need a HD caddy for an Optiplex 960 DT. It is identical to the configuration pictured here:

http://www.dell.com/support/article/us/en/19/SLN288370/en#Fourth_Removal

 So far, from Dell support the only number I get is P/N UJ528.

This doesn't appear to be the correct part as it is different from the one pictured in the article mentioned earlier.

The caddy I need mounts parallel to the motherboard just under/behind the optical drive. UJ528 appears to be the one that mount perpendicular to the motherboard in a cage.

Can anyone out there shed some light on this so I can get the correct P/N for ordering purposes.

Thanks

Steve