Tom,
The only place you can get a new plate is from the copyright holder (i.e. Hartleys), since this plate is what proves the identity and authenticity of your Wayfarer. Hartleys will supply one I believe, but it will be larger and a different shape than the original, so may not fit in the place you removed it from. You might want to consider cleaning up the original as best as you can, then mounting it to something more solid which can be attached in the same place…
Hope that helps!