1998 Chrysler Sebring "loose" wheel

Tires and Wheels problem
1998 Chrysler Sebring 6 cyl Two Wheel Drive Automatic 140K miles

I have a 1998 Chrysler Sebring 2.5L LXi. The alignment is off as if after trying to steer a car to the curb with a flat tire. The car shakes a little on the freeway. When I was getting my tires changed yesterday, the mechanic showed me that the front left wheel is loose (it can be shaken from left to right, but not up-down). The mechanic told me that some part that costs ~$70 needs to be replaced (cannot remember the name of that part, sadly, but I believe it's rubber?), And that the wheel needs to be steadied before I get the alignment done. Anyone has any idea what this part may be and how much should I be expecting to pay for the part and the labor?