I paid $60 for that socket. 10 years ago.
Technically, that nut is supposed to come off yearly in order to remove the impeller in order to grease the splines so impeller can be removed in the future.
There have been some members that have purchased the proper hex size socket. Then cut off the end on a lathe, then welding a proper size piece of pipe between the socket pieces.
Whatever method you use, DO NOT use an impact wrench on that nut. You may be saying goodbye to your gearbox. Hand tools only. There are 2 flats on the shaft for a wrench. Remove the intake grate. Don't try to remove the nut without the wear ring in place. It helps support the shaft while removing that nut. The nut is tight- torqued to 150 ft/lb. plus any corrosion.
Be careful of the end of the shaft- from the nut to the end. It is both bearing surface and seal surface. No imperfections allowed.
Might as well replace the seal while the stator is off.