Damaged Microwave? Plate with metal ring placed inside for 5 seconds

Some might not like the looks; if they're not being used just dig them up. They may have a chunk of concrete that may be as deep as 2 feet.

At my last house I ran a steel wire on both ends then planted string beans with twine from the ground up. Way two many beans but it was fun.

You did not elaborate much on the application side of your assembly but it seems to me that what you want to consider is the use of a brass metal foil. You can learn about and find sources for brass foil by using those words as a search query.

One type of foil is called a "tooling foil" and is available in a 36 gauge (.005 inch thickness). Such foil is easy to cut even with scissors or a utility knife. If you cut out a piece to the desired size it will be easy to bend into shape over the edge of your plastic panel.

You will have to research suitable adhesive to attach the metal piece to the plastic. If it was me I would try the 3M spray mount glue that you would apply to the brass piece when it is flat. Then pick it up and form it over the edge of the plastic panel. You will want to clamp it into place till the glue fully dries. You could possibly use the spring type clothes pins as small clamps.

Note that metal foil may have a coating on one or both sides. You would want to remove this with steel wool before cutting out your pieces. The coating may prevent the metal from making an electrical contact if it is not removed. The coating may also interfere with the adhesive that you use to attach the piece to the plastic panel.

Once the metal foil is adhered to the plastic it should be fairly rugged. Without additional details on your application it is hard to give further advice.