They are for sale at the Brit Library for 12 million.
You will not get them cheaper than that, since that is how you get them and what they cost!
There is another way to get them. What you have to do is hunt in dungeon Blackthorn and collect minax artifacts. You need to collect 50 items with the creast of minax on them and turn them in at the guy right outside of Blackthorn's dungeon. Then you can get an equivalent of the mace and shield glasses, except they're not glasses but other hats or helmets. For a warrior it makes sense to get a metal helmet version of them to get extra stamina protection and the 1% lmc bonus. I think this version is a lot better than the original glasses. However, getting the 50 minax artifacts will take a while. You either have to be able to solo the Blackthorn captains (each drops at least 2 minax artifacts but they're extremely tough) or you will have to kill other monsters in there (evil mages are rather easy, golden elementals, liches, the balron who respawns instantaneously). If you're not going the captains route you'll want to kill as many monsters as quickly as possible. That usually means you won't have time to loot them. Or in other words looting them will slow you down extremely and make getting the 50 artifacts an even more painful process. When I killed evil mages I was averaging about 2 minax artifacts per hour...it's a grind and it's boring as hell but eventually you'll get there.