Magic Items that increase your spell DCs

[Ornery Hobbit]

Which ones (if any) do this?

[Azothath]

when you have a question that revolves around a specific game term like this - it is best to search Archives Of Nethys using their search tool.
example search on AoN
while "DC" will pop up all the time, increase & DC will not.
You can also use a key phrase from a 'hit' and try to find things with similar phrases.
These kind of items are RARE