E-Rigging.com offers Eye x Eye Turnbuckles in Galvanized and Stainless Steel.
Here is the best use cases for the end fittings on this type of turnbuckle:
Turnbuckle Eye End Fittings
Turnbuckle Eye end fittings are the most durable and cost effective ends. Due to their forged permanently closed eye, they are typically used in permanent applications, or in conjunction with a shackle to connect to other fittings. If the load is removed from the eye end fittings, the eye will remain connected securely to the rigging assembly.