I made some halfhearted attempts to find the classifieds over the years and finally broke down and did something no self-respecting man ever wants to do:  I asked for directions.  Yes a search found a brief statement by da bossman to the effect that you gotta be signed in to even see 'em.  So I signed in and posted ads for a Lyle cannon firing mech, 40mm cannon barrels, and upcoming auctions of Hotchkiss 1.65-inch mountain gun ammo.