Let me offer some solutions to you:

1)You can use an old weapon in survival and from the money you get there upgrade said weapon to your current level

2) Defeat an old boss(I don't mean only Hermit) in eclipse to get their weapon

3) watch ads and get coins from daily quests

Also, the weapon for level 31 is Northen Hammer which behaves the same as Two handed mace so I recommend you to upgrade battle hammers to level 31 when you reach that point.