You might try here: http://www.classicboat.com/ads.htm
or here: http://www.antiqueboat.com/boats/Lymans.asp
or here: http://search.boattraderonline.com/search/
or just Google wood or wooden boats for sale.
You might try the paper "boat trader" type magazines, also.
I suspect that you'll have to spend a lot of time searching. The old boat classifieds seem to list mostly restored or well maintained boats in good to excellent condition.
If you are focused on Lyman, OK; but considering other brands might help your search. Cruisers, Inc., for example, made a beautiful runabout in wood at one time. Lapstrake like a Lyman, with a nice flair and clipper bow.
Good luck in your search!