Many parts people are using are home made or bought from cool people like SR forks and Rad bars.
You can get wheels called Yak wheels. I feel they are the best. Its $12 a pair which is really cheap and it will last you for a long time unless you ride like Stan or some maniac << Lmao.
You can get BMX grips , change your headset , brake , bearings , grip tape , etc.
If we change brakes , its Blade brakes only as far as I know.
Any headset is fine as long as it is 1 1/8 " ( I think thats the size. I can't remember how they put it.)Skateboard / roller blade bearings and grip tape from skate shop.
That should help you! Go to the scooter modding thread and you will know all about the different parts.