Look for small or dwarf amaryllis bulbs. Larger bulbs tend to produce longer flower scapes. There are dwarf varieties that will naturally remain shorter.
Place your amaryllis bulb in a large container for stability, since bulbs of any size grown in short containers can topple. Add additional weight by placing gravel in the container to keep your flower from toppling.
Grow your amaryllis in a good environment, since the wrong care causes the flower to grow taller. These plants like cool rooms and become leggy if grown in a hot environment. They become tall if grown in low light conditioners, so make sure your plant has access to light to help keep it on the short side.
Cut back on fertilizing your plant when it begins to grow a flower scape. Choose a low nitrogen fertilizer, since excess nitrogen promotes tall flower stalks. Once your amaryllis finishes blooming, resume fertilizing.