Here is my suggestion:
I see that there there are several Kappa Sigma bar signs on EBAY:
http://search.ebay.com/search/search...trypage=search
How about emailing the seller and saying, "Hi, I saw that you have a Kappa Sigma bar sign for bidding on? Do you carry other fraternities also? I am looking specifically for Lambda Chi Alpha".
You might be in luck.