You can buy another unit, the Super UFO, which has 32 Mb, it has a floppy drive only, no parallell port.
Or you can buy a Super Wild Card DX2. It's 190 USD (shipping included) for the 32 Mbit version, or 210 for the 64 Mbit one.
If you want to upgrade it, it'll be tough to find the right memory modules. You have to check with the other guys on the board...