Are there any species of turtles that won't eat fish?

It will be difficult but not impossible to find a turtle which fits your needs.

There are some main factors you need to focus on: temperature and water quality. The temperature will be important for your turtle, the water quality for your fish.

You need to find the kind of turtle, which will survive in the temperature region you live in. If you decide to move the turtle inside during winter, you would have more options.

And you need to calculate, if your fish will survive the decrease in water quality a turtle would cause. And if you are willing to buy additional equipment to make the water more suitable for the more sensible fish breeds you may have already. A general rule of thumb in turtles is, that they produce 3 times the waste fish would do. So if you use a filter for your fish pond, you would need a three times bigger for a turtle pond. Special focus will be about the nitrite, nitrate and ammonia key values. (Aims: nitrite not notable, nitrate below 50mg/l and ammonia below 0,4mg/l.)

You wrote about goldfish: They in general love cold water and, in ponds deeper than 1,5 meters (if I remember right...), could even survive frost periods. Famous turtles, like red eared sliders and yellow bellied sliders, would not tolerate such deep temperatures this easy.

The shape of your pond need to be appropriate for a turtle. They need some flat bank at one side, so they could walk from the cold bottom to the surface to breath. Because they are hematocryal animals, they need some warmth provided to make the body moving more easy. They would do this by basking (sun bath) but need a less difficult way to reach the warm place in the sun. Also, you would need some barrier for the turtle to stay in your pond. A mesh wire would not help, turtles are able to climb them, even 1 or 2 m high (and crack their shell by falling down the other side ...)

If you provide more information about the temperature in your region over the year, I could give more detailed information about the possible turtles and if they eat much fish or not...