Monochrome LCD sources
You simply need to keep looking on all the major vendors sites - Digikey, Mouser, Farnell, RS, etc. If you can't find anything suitable between them, then it's unlikely there is anything off the shelf (you can talk to display manufacturers for a custom option if the quantities are worth it)  

I typed in "LCD" to Mousers search box, and I got a load of options that may fit your requirements. Here is one example 128 X 64 monochrome display for &lt; £10, although I don't know if it has an SPI/I2C option (plenty more  here):

 

Here is a monochrome 128x64 SPI option at ~£12:

  

Also, if you found a suitable colour display, why not just use this as a black/white display?

For salvage, I can think of things like photocopiers, handheld test equipment, old PDAs/personal organisers (e.g. Palm Pilots, PSION products) that have such displays. Maybe a search on eBay might give you some other ideas.   

  

Parallel connections and FFC/FPCs

Although some of the parallel connection options can look daunting, they are not so hard to hand solder. Some are designed to be soldered directly (google "hot bar soldering" and "FFC soldering") and some are designed for a suitable socket. Here is an example of of one of my prototypes which used an FFC based display:



The soldering is pretty easy with plenty of flux and a drag soldering technique.