looking for a mario galaxy type gravity (if in wrong area please move)

Hi just wondering does anyone know an asset that can replicate the gravity/physics of mario galaxy im asking as i want to make my huge planet round so players can go any direction and still get from a-b etc but i want to make sure they “stick” to the planet,arrows have a curve etc
The reason i want to do this is so i can have a fully interactive space scene in my games nights,realistic launches,eclipses etc
Another example is kerbal space programme

The planet will be huge (in unity terrain like 100k by 80k mabey bigger) so there wont be an obvious curve like how earth seems flat from the ground

Can anyone point me to a good asset that does this sort of gravity/physics ?
1611815--97964--$galaxy2review.jpg

Check out this tutorial: http://armedunity.com/topic/6916-faux-gravity-walk-on-planets/