Plenty of places sell the 12 sided D4's.
And honestly, on my rogue, at +13 to hit 1d4+10 + 2d8 sly flourish w/sneak vs a raper at +12 1d8+10 + 2d8... I'll take the better to hit for a few points less damage. For multiple weapon dice attacks, the doublesword does start to have appeal, but I think giving bigger damage dice with the rogues virtual +4 proficiency with daggers just based on race alone without a feat would be broken.
And honestly, on my rogue, at +13 to hit 1d4+10 + 2d8 sly flourish w/sneak vs a raper at +12 1d8+10 + 2d8... I'll take the better to hit for a few points less damage. For multiple weapon dice attacks, the doublesword does start to have appeal, but I think giving bigger damage dice with the rogues virtual +4 proficiency with daggers just based on race alone without a feat would be broken.