Changing a weapon's size?

[McToomin]

I've been outfitting a cohort, and I decided to spend most of his money on his weapon. I made it bashing so that it will deal extra damage, but I didn't have enough yet to buy some Strongarm Bracers (to wield a weapon 1 size category larger than normal). I'll be saving my gold until I can grab those.

My question is, is there any way to permanently grow the weapon so that it's a larger size? It's Bashing Flaming and has a Crystal of Return, so it'd be a shame to have to buy all of that over again just to make it larger. I've looked all over but I can't seem to find anything. The only way I could think of would be to hand the weapon to someone else, cast Enlarge Person (and I'm not a caster), and then cast Permanency, and then take the weapon back. But it seems like there must be an easier way, and that I'm just not seeing it. Can anyone help? Thanks!

[Zale]

There is the Enlarge Weapon spell from Complete Scoundrel.

I'm not sure if your DM would allow you to Permanency it, but that spell does what you ask.

[Greenish]

There's the Sizing property, but that's 5000 gp.

[McToomin]

Those were both really helpful, thanks!

[holywhippet]

The mighty wallop spell and greater varient can increase the effective size category of a blunt weapon without actually making the weapon any larger.