It was a wondrous store that had an entire wall devoted to chemicals such pyrogallol, ferric ammonium citrate, silver nitrate, ...
As far as film developers I have used the Beutler developer extensively with Pan-X. A truly wonderful combination. D-23 was also a favorite. I have made my own Rodinal starting with paraminophenol HCl. At the present time I use a concentrated developer based roughly on Paul L. Anderson's Kalogen. He designed this developer to replace Agfa's Rodinal which was not available during WWI. This developer was sold commercially for a few years. It uses Metol, hydroquinone and sodium hydroxide. Here is the page from his notebook http://notesonphotographs.org/index.php?title=Kalogen. I use it 1+49 just like Rodinal. When diluted 1+11 it works like Dektol for papers. Sort of the schmoo of developers.
I subscribed to the Dignan news letter and tried many of the developers that appeared in it. Things like some of the Crowley developers, POTA and Microphen.
At present I used either the Kalogen variant or HC-110 for film, sometimes D-23 for Pan-F.