this is all that i could find outside of gumtree (used and cheap), but there are some good ben q and others there.
I would really opt for the best 24" that you can afford and not to go over a 5ms response time, in my experience that is all that you really need and anything faster than this is for those with really keen eyes and who earn money doing competitive gaming.
if there is anything else let me know and sorry for the wait time had to visit family while in town.
21 inches is fine. Considering tablets with much smaller screens as 1920x1080 and higher.
Smaller screen = better pixel density
But its true that text will be a bit small but if it is too bad you could increase the DPI but you shouldn't have too