So I am having issues finding the stuff in the pic. Is there something else that is polish that works or am I going to have to use nail polish?
DESU Future isn't that strong. If possible you should look at lacquer top coats like Testor's lacquer clear cote. Given, not all plastics are safe against lacquer, even if the top coat is specifically devised for use on plastic models.
Regular acrylic does its job fine. It's not like you really need it any stronger for the typical loose joint
Have you tried lacquer on die-cast joints? We've yet to know how to tighten those damn things...
I have no idea for die cast. I doubt modeling lacquer top coats will adhere well to metal. If it's poor quality die-cast it's probably just warping and wearing too quickly. My recommendation is to try elastidip if you're feeling adventurous. Sand the surface you want to coat to give it a rough finish then brush a few layers on. I have no idea how well it will stick to metal, but a rough surface will help with adherence. It dries much thinner than it actually looks so you may need to use a few layers.
Just keep in mind that the medium is toxic, so you probably want a proper respirator (same kind when using lacquer paints) if you plan to have the can open for more than a few minutes per day.
Any clear acrylic paint will do the same job. The glossier, the longer lasting.
People need to stop listening to /toy/'s outdated advice when it comes to Future and floor polishes.
Never use nail polish. As other anons said, you want a clear acrylic coating. Nail polish is more like a solvent, it has acetone in it and is prone to discoloring, messing with the plastic's surface, and getting sticky in warm temperatures or with age.