You might be able to find some cheap oil drums for practicing the barrel race at home. But practicing and running into the barrels can lead to injuries for the horse and rider. Plus if your cowgirl is small, she might not be able to maneuver the oil barrels into position.
The American Heritage Equine Tight Turn Barrel Flexible barrel racing barrels are three collapsible easy to move carry barrels. These 3 collapsible barrels fit conveniently in a zippered bag with a handle and can easily go with you anywhere. They have a weighted bottom to stay in place and are the same size as a regular barrel.
Light enough that any cowgirl can move effortlessly.