For continuous usage in a browser, I'd prefer following Tetsujin's recommendation and try a standalone but supported Flash player, such as Newgrounds'.
#Add adobe flash player to google chrome Offline#
Note: In my case, the application using Flash works offline and should present minimal security risks. Note: the linked page mentions mmc.cfg, but my Flash folder had a mms.cfg file instead maybe it was a typo, but in any case I added the EOLUninstallDisable=1 line. I just tested an offline desktop application which had stopped working, and it works again. Copy the Flash directory with the modified binary to its original location.Rename the Flash directory (to avoid permission issues) to Flash.bak or something else.