If you are referring to the Sleeper function of the OEM Leather Holster of any BlackBerry model (as long as it's the QWERTY model) to work with your Curve, then you are definitely correct. But, they are different in size. If you wouldn't mind how your holster would fit with your Curve, purchasing any OEM BlackBerry Leather holster would be okay.
Shown in this thread
, the difference between the 8300 and the 8800 Skin. This should give you an idea of the size difference if purchasing the 8800 Leather Holster for your Curve.