Contact HAAS for memory upgrades. You may be able to get 'off-brand' expansion cards for considerably cheaper, but I don't know about those.
You can make your own cables. Just buy some RS232 cabling and attatch the 9 and/or 25 pin connectors. The manual has the wiring diagram.
Keep in mind, the longer the cable to the machine, the more chance for trasmit errors and interfearance. A slowdown in trasnfer rate will help, as will properly shielded cables.
How are you trasnferring files to the VF7?
'Rekd