show the cursor or make a custom cursor

the game itself, the mouse is the look of the player (mouselook) so that when I go to the scene of the inventory eg I need the cursor … can someone help?

You can use Show Cursor under Display, under Render. If you want to toggle it on and off you could use this:
ON

 import bge
bge.render.showMouse(1) 

OFF

 import bge
bge.render.showMouse(0) 

Monster also made a custom cursor guide. You can find it here.

Sure:
Cursor and Cursor Library

3D Cursor