unfortunately tonio's answer is not correct because in his example we have recall that for any ideal of we define
anyway, to answer the question, you can choose then it's easy to see that is the set you're looking for.
Why "unfortunately"? My idea was wrong but, perhaps, it could push the OP in the right direction. Anyway, she/he now has the correct answer and can compare. Nothing lost, all is profit. Thanx for the correct answer.