Dow Corning offers Silastic MDX4-4210, a two-component silicone adhesive that has a tensile strength of 5 MPa. NuSil offers MED-1000 one-part silicone adhesive and MED2-4013 two-part silicone adhesive, which have similar strength characteristics. Momentive Performance Materials, Rhodia, and Wacker offer alternatives as well. These adhesives are listed as tensile-strength materials. Their operating data are acquired by molding a dog-bone tensile bar and pulling it 180° apart until it breaks. The breaking point determines the tensile strength. Bonding two pieces of a substrate is tensile shear strength, but adhesion depends on the substrate itself as well as the surface area. Most vendors cannot test all combinations and substrates, so evaluation of these candidate adhesives determines if they will reach 4–5 MPa, as you require.

I recommended these materials based on their tensile strength. If a material has a lower tensile strength, it might tear cohesively in the application, leaving silicone adhesive on both substrates. By selecting a high-tensile-strength material, the cohesive strength of the adhesive will be above your minimum value, so that you can focus on the actual adhesion of the silicone adhesive to the substrate.