There are some alternatives at the very least. Despite the short list there are certainly functioning contenders for the fifth generation stealth fighter jet fleet but there is non for the F-35B. The uniqueness of such an aircraft is underestimated. Its a VTOL fifth generation fighter jet. No equivelant exists, or will exist for the foreseable future. When it comes to air defence we are indeed lacking behind quite a bit, but there is already pre-existing projects that already provide short-medium term solutions with long terms solution being well on their way to being developed. Honestly in this case i would bite the bullet and just go for Patriots instead of S-400, purely for the F-35B's.