I am not sure if you can set the switch to pull the vlan.dat file from the PC Card but you can enter the vlan information in regualr config mode on IOS switches. The command format looks like the following in the normal (running or startup) config file.
vlan 20
name VlanName
This functions the same as the vlan.dat file and is actually preferred because if redundant SUPs are used the Vlan database is now synchronized between the SUPS where as using "vlan data" they are not. Also, as you modify Vlans using config mode the vlan.dat file is changed acordingly.