Ethanol 95PGF4
Perfumer's Alcohol will be the above with additives like monopropylene glycol and isopropyl myristate to act as fixatives for the perfume oil and to prevent the alcohol flashing off too quickly.
Perfumer's Alcohol is a phrase you can search for on popular online retailers websites to get something that will be suitable without fully understanding the science. Lord knows, I don't. What I do know is that a blend improves with time. 60% alcohol, 40% witch hazel. Drops of EO. Start out with 10 drops per 100ml. Don't be tempted to overdo it. Light scent is good for a post-shave astringent. Glycerine is good to add. You can buy it at the supermarket as it's used in baking.
Some websites talk about using Turkish Cologne as a base "because it is 80% alcohol". It's actually not, it's usually 80 degrees proof (so, about 40% alcohol). Laughably, some sellers cite "80% proof", like that's a thing. At 40% any blending with Witch Hazel will render the aftershave a bit light.