I've found loads of old Watchtower's and Golden Age's for sale on www.ebay.co.uk. Then just type watchtower into the search.
Most of them date from 1912 through to the 1940s, and are currently at about three pound each, but the auction finishes in about 5 hours so be quick.
Theres bound to be loads of good reading in these to find weird old policies, and you can imagine witnesses faces if instead of quoting 'apostate' liturature to them you just use watchtowers.