We have, in the local grocery store near me, an item called 'Laura's Lean Beef'. This is a regular, big name chain grocery store.

Organic fed beef, no antibiotics, and quite tasty. maybe ask your local grocery store manager to order some. Grocery store managers are generally quite amiacable in regard to good new things they can sell.

They also sell Amish chicken here, same deal, organic fed, no antibiotics.

And then of course there is fish. Fresh water farmed fish generally does not have any mercury content.