Where can I get good Bismuth trioxide

Where can I get good Bismuth trioxide? For many people this is a strange object, and here's the introduction:

Bismuth trioxide, yellow powder, insoluble in water, soluble in acids. It can be reduced by carbon and hydrogen. The pyrolysis of bismuth nitrate is obtained. It is used to make metal bismuth, catalyst and bismuth oxide superconductor.

Mainly used in chemical industry (such as chemical reagent, bismuth salt manufacturing, etc.), glass industry (mainly used in coloring), electronic industry (electronic ceramics, etc.) etc. Among them, the electronic industry is the most widely used industry in the application of bismuth oxide, mainly used in the fields of pressure sensitive resistance, thermistor, oxide arrester and picture tube. In addition, Bi2O3 has high refractive index and dielectric constant, significant fluorescence characteristics and inertial-water. Therefore, Bi2O3 is a potential photocatalyst for decomposing water and degrading pollutants.