1. 17-β Estradiol, cheapest for 155 yuan/10g. Search for CAS 50-28-2 [1] to find it on Taobao, don't search for the keyword estradiol.
2. CAS 54182-57-9, Carbomer 980 [2], 55 yuan/10g. Don't be cheap, there are fake ones which will not form a gel. I purchased imported ones which were expensive.
3. Triethanolamine [3], 11 yuan/g. Don't be cheap, the cheap ones are yellow with a weird odour.
4. Distilled water, free? Just use drinking water instead.
5. Alcohol, 15 yuan/L, 75% or 95%, as long as it's above 60%.
[1]: CAS = chemical abstract service, a registration code used world wide to identify chemicals.
[2]: A type of thickener/gel maker.
[3]: A compound used in many skincare products. Will cause irritation after prolonged use.