I'm not sure what part of your HID is loose, but if its the actual bulb in the housing socket, why don't you try cutting a thin strip of double sided tape and attaching it to the base ring of the bulb and then sitting it snug in the housing. If something is loose or doesn't fit, there are many ways to remedy it. Take a few pictures of the problem and post them up. Also would like to see how the actual lighting looks.

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1990 190E 3.0L