HostFS allows you to simulate an SD card on the Palm.
Right click on the Palm OS Emulator (POSE).  Select Install Application/Database --> Other...
Select the HostFS.prc program and click Open.

The HostFS extension is now installed.
Perform a Soft Reset: right-click on POSE --> Reset --> Soft Reset.  Click Reset.
After the OS reloads, save the emulator profile.
Now, right-click on POSE --> Settings --> HostFS

Select a local file system directory for each desired slot and select the Mounted checkbox:

Now the Palm will allow you to browse the contents of the local directory as if it were an SD card:

Note: The path ".../<sd_dir>/PALM/Launcher"  will be created by default and needs to remain in the local directory.