I bought 8 wooden fence posts (4x4 rounded edges) theyre flat sides but the corners are round. They're 12feet long and $4 each. I like them like that because they will roll if pushed but will stop rolling fairly quickly, so the horse is less likely to be tangled up if it falls. Also the lighyer wood is better if for minis, they also make heavier versions of these fence posts that I think wouldnt be knocked off easily enough. I got mine at home depot, im sure any similar store would sell an equivalent.