Altair 680 Memory Expansion Kits?

[Bill Degnan]

Thought I'd ask...I am looking for a new 4K (or more) RAM expansion kit 
with schematics for an Altair 680b that I can build myself.  Ideally the 
kit would build an expansion card and operate like an old RAM card.  An old 
vintage RAM card would be fine too, but that'd be expensive and I assume 
there are none to be found at this point save the rare luck.

I am not sure if you can still get them from stockly.com.

Thanks
Bill