A question has arisen if shopping advice posts is off-topic and should be kept closed.
I realise that this is not a question on physics, but how does one otherwise ask the fellow physicists for this kind of information? Experimental physics is to a large extent about choosing the right makers. Besides, the question 12466 is not just about where to buy these liquids, but mainly about why they are so rare on the market. I have never worked with them, so do not know, and was asking for help. People experience in refractometry / microscopy might have been able to answer question 12466.