433 MHz Antenna - Balanced Dipole + Balun?
Full size antenna options would be a ¼ λ vertical monopole with one radial or a ½ λ horizontal / vertical dipole.

Holes are to be drilled in the enclosures to lead the elements out.
The ground point on the PCB is to be connected to the metal enclosure.

The unit may be oriented to have the dipole horizontal or vertical.