Katmandew - That is quite the pickle, if you want to diversify (as there is really no good way to do so other than selling). But you do appear to have a good handle on where everything is (current profitability, potential buyers, etc).
Though, with private stock, there are a number of issues, that you have identified, especially if you are employed by it. As you may be restricted in who you can sell to (either by agreement as well as Sub S restrictions). As well as it may send a message that you don't want to send. I know that you mention that the people that you could sell to, aren't buying at the moment. Have you attempted to talk to them about wanting to diversify (and reduce your concentrated position; as that generally goes over better than just saying I want to sell out)? As I'm not sure who the current ownership group is (if it is a family group, all employees, just executives, or something else), or if there is an esop. I'm familiar with a few such banks in my state, and usually there is a "president's desk list" or interested buyers (if it isn't just a family group).
Though with the industry as it is, if there hasn't been any already, the bank will probably get some offers to purchase it (at some multiple of TBV), as it seems like they just keep consolidating for economies of scale (which is understandable, as due to the technological and regulatory costs). And if there is only a few owners, and they are getting towards retirement age (in their 60s), most likely the stock is a significant amount of their net worth and they are most likely thinking about how to diversify or liquidate it themselves. And even if not, there should be some consideration of it (potentially as succession planning).