I have a microscope from my uncle, also a doctor, which came with a ton of slides he prepared. If you don't know someone who had to build that collection of their own specimens in med school, you can get all kinds of prepared slides commercially:
https://www.amazon.com/dp/B0836SH17X
> Human Cell Mucus Membrane Smear 72 Dense Connective Tissue Section 73 Ciliated Epithelium Section 74 Oesophagus T.S. 75 Stomach Section 76 Small Intestine Section 77 Lung sec 78 Liver Section 79 Kidney Section 80 Spleen Section 81 Pancreas Section 82 Urinary Bladder Section 83 Ureter C.S. 84 Ovary Section 85 Testis Section 86 Oviduct T.S. 87 Uterus Sec. 88 Tongue L.S. 89 Trachea C.S. 90 Epididymis sec. 91 Large vein sec. 92 Thymus Sec. 93 Human Blood Smear 94 Motor Nerve W.M. 95 Spinal Cord C.S. 96 Human Hair W.M. 97 Artery and Vein C.S. 98 Arteriole C.S. 99 Human Skin Sweat Gland Section 100 Skin of Human(show hair follicle) Sec.
Also, one cadaver can generate an awful lot of slides. Each slide requires on the order of a microliter (1/1000 of a milliliter) of material, and a good microtome can cut samples with a thickness of a few micrometers (1/1000 millimeters). Essentially all medical students go through an anatomy class involving the dissection of a cadaver, and Google says there are 3.8 million doctors in China, so even with a generous assumption of 20 students per cadaver and a static field (it's not) with 50-year careers, that's still several thousand cadavers per year.
This strongly suggests that “organ donation” in China is as-needed and on-demand from political prisoners and ethnic/cultural undesirables.
> Although variolation eventually declined or was banned in some countries, it was still practiced in others. "Buying the smallpox" was still practiced in Sudan until the late nineteenth century. However, variolation survived longer elsewhere. During the World Health Organization's Smallpox Eradication Campaign, vaccination teams came across variolators in remote areas of Pakistan and Afghanistan and their samples were confiscated. In the early stages of the campaign, live virus was detected in some, but as the campaign progressed variolators could not replenish their stocks, and although virus particles were detected in some samples, very few contained live virus. Our knowledge about the survival of smallpox virus suggests that passage of time makes it extremely unlikely that any infectious samples have survived.
Not sure, but I'd hazard that someone driven enough to break into one of the few remaining facilities holding live stock of smallpox would also probably be willing to infect themselves with it so as not to worry about preserving it.