1998 Jeep Grand Cherokee Question: We have a small coolant leak near bottom radiator.

No Check engine light radiator and reservoir are holding fluid and not needing refilled much...but we have been having a small leak it runs from what my husband thinks is a small seal leak at bottom of radiator...Is this a costly fix @ a repair shop? and What might this leaking Part be called for sure?
I know it slowly leaks and then build up in a plastic part under bumper and radiator then it spills into the bumper and leaks from driver side bumper...but the origin of the leak is near the bottom of radiator..Please help I need to budget to fix this problem. Also It's not over heating and We've replaced hoses and radiator and water pump all since 2008.