Dik, I have a round stool riding on four casters. It has a parts tray underneath and the height is controlled with an adjusting handle, it has a pneumatic feel to it, quite comfortable. I got mine from Sears, it is a craftsman branded stool. I wonder if you could order one from the states or have somebody pick one up for you down there. Others have taken over the Craftsman line so it is possible someone else is making them as well.
Good luck, they are handy to have.