If you don't mind some glitchy graphics (temporary), you're 6th Slot item being duplicated, and you're Hall of Fame being permanently screwed, there's alway's 'M, who evolves into Kangaskhan. I've heard there is a chance of your game save getting deletd, so be careful. 'M is a glitch available by doing this:
Go to Viridian City
Talk to the Old Man and let him capture the Weedle
Fly to Cinnibar Islands
Surf on the side of the island that is half land/half-water.
Different Pokémon appear, a MissingNo. (advised not to catch), Pokémon above Level 100, and 'M. Catch 'M and level him up. Also, after you catch 'M he'll still be there, catch him again, you'll get a Ditto. So once you've leveled up 'M he'll evolve into a Kangaskhan. However this is risky, so try Safari Zone if you want to make sure you're safe.