LST or Low Stress Training in the GROWFAQ
Any wire that won't rust will work good.
Or for that matter string works great!
just poke some holes in the sides of the top of your bucket and tie one end of the string to the hole then the other end to the plant.
(Of course remember to use the techniques described on that Grow FAQ page)
Basically near the middle of the plant you tie a string
(wire) and tie the other end to your bucket.
Then on the OPPOSITE side tie a string higher up and pull SLIGHTLY down until you have bent the plant SLIGHTLY.
each day you can apply a very small amount more pressure on the upper string until you have the thing bent sideways.
It will correct itself re orienting the top toward the light in short time.
This will reduce the height of the plant without damaging it and it will stay shorter as a result.
The key is to anchor the plant with the lower string
this will cause the plant to bend rather than the upper string just pulling the thing over and uprooting it lol.
Hope that helps you, just read all the ways different people do it at that link
and adjust to suit what you have to work with and what you aim to accomplish.