You must be new here... There were several giveaway posts a few weeks back and if you check CableMod replies and Drop top, you'll see that both companies were very kind sending freebies to people. There might be other companies too but CableMod and Drop were the ones I keep up with

I should clarify that I wrote that for freezing in general, I've only worked with sperm cells and the list is sort of the less toxic to the most toxic

There are two types of cryoprotectants: extracellulars and intracellulars. Extracelullar cryoprotectants are impermeable to the mebrane and protect the membrane of the cell and they can be sugar-based (glucose-based, lactose-based, others) or protein based (egg yolk, albumine, others). Intracellular cryoprotectants are permeable to the membrane and prevent against cryoinjuries (ice particules forming inside the cell and then breaking the membrane) and they can be glycerol, dimethylsuffoxide, dimethylacetamide, ethylene glycol, methanol, methylglycol. There are more cryoprotectants but these are the most common used

Edit: The cryoprotectants I've mentioned are all that I've used on sperm cells. Some might not be viable for embryos

Mice and zebrafish are the most common for disease studies. Researchers have the whole genome for zebrafish mapped, so as someone already explained, they can use knockout zebrafish and implant the cancer cells on the specific tissue or they can alter the DNA and make the fish produce the specific cancer cells needed

I like that the Esc key is named Panic