These are examples of thin metal plates made of steel that are easy to obtain and react to magnets. It is recommended to use plates 0.3 mm or thicker, as thinner plates may have weak magnetic response.
Plate 1 can be obtained in large quantities and is suitable for assembling many paper models. Plates 2 and 3 are recommended for assembling only one or two paper models.
Please refer to the website link for detailed features and pricing information.

Product Data
1) Paper Fasteners
Website: Amazon
Material: Steel
Feature: Can Be Disassembled into Two Pieces, Effectively Providing More Than Twice the Number of Metal Plates

2) Snap-Off Blades
Website: Amazon
Material: Steel

3) Washers
Website: Amazon
Material: Steel