Idler Arm Install

I cant say which idler arm you have but I had the opposite problem when I changed my idler arm. The bracket on my k member was too narrow and I had to widen it using a long bolt and a couple of nuts to spread it open. I stretched it out until the point where the idler arm would hold itself it place but I could still tug it out if I needed to move it. I wouldn't be happy if my car had that much play there. Have you tried tightening it down to see how much the bracket compresses? Or maybe consider running some sort of spacer/washer to take up the slack