You can buy one that’s pressure rated for lifting weights on etc. They don’t burst when you sit your ass on them for 10 hours a day over a few years.
But good news for you is that sit, stand, curl yourself up in a pretzel, none of it will make a diff to ‘moving when you’re old’. This is just the inanity those without meaningful health issues engage in.
If you have fitness goals they can be pursued. Certainly sounds like you could benefit from balance and core strength. But this generally does require getting off your derrière, and is simply a lifestyle choice. Feeling better with a clear mind and body. The idea that exercise can stave off disease or aging is one particular to our times. It’s just the age old veneration of athleticism in a new format.