Does anyone know where I can purchase kitchen acbinet door pistons that are all metal, instead of plastic? Costco has some on their cabinets and I want to retrofit them on my cabinets.

You need to find a kitchen company that sells cabinets. These higher end hinges and drawer closure devices are not typically found in the big box stores as they can be quite expensive.
Also you may have difficulty in getting something to work with the current hinge holes and door style you have. Be sure to just purchase one or two sets until your sure these work. A few cabinet shops do not allow for returns seeing they typically only sell to contractors. Be sure to check.