I don't use pskeys, but I believe it could be changed to use RAM store. Take a look at documentation available @ csrsupport.com.
On a side note, I recently acquired a DELL Trumobile 350 bluetooth module. It has a BC4-Ext w/ 8Mb flash inside and supports BT 2.0 specs with enhanced data rate (upto 3Mb/s). Even with slower uart speeds, the radio is supposed to transmit for shorted periods of time when communicating with other BT 2.0 devices, thus better power consumption. It also small in size, so could be a good fit inside the Zaurus. However, I have a problem with locating its pinout (it has a 10 pin connector and six additional soldering pads on the back). The module is manufactured by USI for DELL, but all design is done by CSR itself, so I'm sure it could be switched to uart mode. Here in the US, it's just a slightly more expensive than usb dongles, I think I paid approx. $20 for this module. Can you find one in Russia at reasonable price?
-albertr