Found a pair of Monitor 10B's for sale at the outfit below, They have a bunch of other interesting vintage used speakers. The 10B's are roughly half way down the page. Below is the description found on the website.
Manufacturer: Polk Audio
Model: Monitor Series
Condition: (8.5-9.4) Excellent
Price $ 250
These speakers come packed with 2 6" woofers with a 10" passive radiator, a 1 1/4" dome tweeter and vinyl wood-grain cabinets (rosewood)