Dear Fabrice,
I don't really think such a brick exists (unless Yves corrects me).
But you can obtain the desired effect if you deform your mesh during
the assembly of you pressure Neumann term.
For that you need to define your problem not on getfem::mesh, but getfem::deformable_mesh.
Subsequently, you can place a single line in the assembly of normal_source_term_brick
getfem::temporary_mesh_deformator d (your_mesh, mesh_fem_of_displacement, displacementVector);
So, this way your pressure term will be assembled on the current configuration.
However, the above trick is not fully consistent, of course, as it won't add the corresponding stiffness
contribution that comes from the changing geometry. So, your "follower" pressure will be added in
explicit sense. If you want fully implicit procedure, I think you'll need to create a new brick.
Best regards,
Andriy