Eventually I will be stocking up on a few choice peripherals for the Portfolio, including a system RAM memory expansion card (with peripheral port pass-through, kind of like an ur-Sonic & Knuckles experience), a serial interface, and a diagnostic interface produced for licensed repair shops and peripheral developers, all due to the diligence of a single vendor, aptly named Best Electronics, who's maintained stocks longer than the original company stayed in business.

http://www.best-electronics-ca.com/portfoli.htm