I was there in 1998 and with a different tour company. There is, or was, a gift shop attached to the museum where you could purchase reproductions of the warriors in various positions and sizes, Tang horses (also reproductions), and videos of movies about the rise and fall of the emperor. Along with the usual touristy kitsch. They shipped our purchases and guaranteed their safe arrival. I can attest to that, because my Tang horse arrived damaged and they replaced it.
If you would prefer to order online, you could wait and see how big a piece you wanted by seeing what's available in the shop. A cousin of mine has a kneeling archer that is full-size, that is full-size of the statue which is, I believe, 5/8 human size.