When selecting Quick Connect Terminals it is ideal to use the terminals recommended by the manufacturer. Take for example part
84-8511.9620 a switch from EAO as seen in this snippet from the datasheet.
In an ideal world we would always be able to follow this rule of thumb, but situations are often less than ideal. As seen above there are two dimensions listed 2.8mm and .8mm. The first is the width and the second is the thickness of the insertion tab. Using those measurements an equivalent can likely be found here Connectors, Interconnects | Terminals - Quick Connects, Quick Disconnect Connectors | DigiKey.
If you cannot find the exact size you need, a slightly smaller size may work, but the connection would not be as snug, you we need to see if it would work for your application.
To look terminals up by size or other factors use the filters on our website, such as the examples shown below.