If you cant wait that long, then enter the Create-A-Legend screen and intentionally make a wrestler with poor attributes (stats all zero). Defeat him repeatedly in ladder and cage matches to get three Green Coins with each win.

Unlock Andy Kaufman
To unlock Andy Kaufman, select career mode and choose Jerry Lawler. Defeat Andy Kaufman to unlock him at the shop.

Unlock Big John Stud
Defeat Big John Studd in Career Mode to unlock him at the shop.

Unlock British Bulldog
Select career mode and choose Dynamite Kid. Complete career mode to unlock British Bulldog at the shop.

Unlock Bruno Sammartino
Select career mode and choose Hulk Hogan. Complete career mode to unlock Bruno Sammartino at the shop.

Unlock Owen Hart
Select career mode and choose Bret Hart. Successfully complete career mode to unlock Owen Hart at the shop.