You can get your own Carnaval gear, as well as musical instruments, colorful decor and water guns/water balloons at the many street stalls in Oruro.
This sweet-looking elephant water gun (below) is a backpack that kids can fill with water and then wear without having to "reload."
And if you want a cholita skirt, you can find all kinds, from shiny to matte, patterned to solid and everything in between.
A wide variety of musical instruments are available, as well.
Here are some more views of the markets: