At this stage of the season teams start to have injuries and one of thew quiclkest and cheapest ways to fill the role is through free agency.
Pedro Gabriel is available. While he can hit fairly well he is a liability behind the plate. His market is limited.
Terry Wilson would be a decent platoon C to face righties and his D is good enough to not hurt. He should have some interest if teams need a C.
Placido Eusebio is worth mentioning because he is has a defensive presence. He can call a game and keep runners honest. Sadly his dedication to defense caused him to skip some BP, and it shows.