I think it is better to be safe than sorry with the inert gas when working with lysergic acid--meaning that all of the reactions should be done in inert gas and in the dark. Any toxic chemicals present would be present in the final product in only very tiny amounts per dose, but if you don't eliminate the impurities then you could throw off your ratios and have difficulty measuring yields.
Acetonitrile and trifluoroacetic anhydride are easier to get than POCl3. US Patent 2,736,728 describes the process: https://www.thevespiary.org/rhodium/Rhodium/chemistry/lsdpatent.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/lsdpatent.html)
(about halfway down the page). I would think that they are less suspicious too. I wonder if it would be safe to use lysergic acid monohydrate instead of dry lysergic acid by adding an extra molar equivalent of trifluoroacetic anhydride.