Here's a Gundlach No. 612-SW SEAM WEIGHT.
"The Seam Weight is used by professional installers to make better carpet seams! It has a perforated white plastic base with enough air space between the base and steel weight to allow for heat and moisture to quickly dissipate. This weight outperforms any tool box tray by exerting uniform pressure without discoloration from excess heat retention or rusty trays. The white plastic base glides smoothly over the carpet and will not snag like plywood or a tool box tray."
Buyer to pay actual shipping from 97401 (check the different options to see which is best to your location).
If I unscrew the handle (four Phillips screws) I can fit this into a USPS Medium Flat Rate Priority Mail Box and ship it to you for 16.00. If you'd like to go that route let me know before you make the purchase and I can revise my listing for you.
Please email me if you have any questions.