You will not find extra longs except among cartridge collectors. It is an obsolete round that went out of production in 1935.
In THEORY- a rifle chambered for /22 Extra Long will also shoot shorts, longs, and long rifles. I would STUDIOUSLY avoid any high speed/ ultra/ golly gee .22 ammo in a rifle that old. The Extra Long was originally a black powder cartridge, with 6 grains of powder.
What we have here is... failure- to communicate.