Like KRyan says in his answer, it's unlikely there's a way to wield a double weapon in one hand yet benefit from the double weapon as if it were wielded in two hands. However, for a dragonsplit alternative—both because the the Monster Manual IV doesn't provide the weapon's cost and because dragonsplit is a really dumb name—, there's the crescent knife (Dragon #275 43, 44) (20 gp; 1 lb.).
Illustration by Kennon James and David Day.
The crescent knife, an exotic weapon, appears only in Andy Collins' article "The Right Tool for the Job" even though most of the article's other weapons are reprinted in Sword and Fist. It's a Small melee weapon in Dungeons and Dragons, Third Edition terms (therefore the DM likely making it a light weapon in 3.5 terms) that deals 1d3 points of slashing damage and ×2 damage on a critical hit. Hiding behind these unexceptional statistics is a description that's pretty crazy:
This weapon, which resembles a crescent-shaped blade affixed to a crossbar handle, allows its wielder to make two simultaneous attack rolls (using the same modifier) each time he attacks with it. Each attack is resolved separately. (44)
There's even errata for the crescent knife:
The crescent blade should have an additional phrase added to the last sentence, making it read as so: "Each attack is resolved separately, but only half the applicible Strength bonus to damage is applied to any hit." (Dragon #277 120)
(As no other weapon in the article uses similar mechanics or has a similar name, I assume the editor meant crescent knife not crescent blade. Ask the DM. Further, as a Dungeons and Dragons, Third Edition item that was never updated to 3.5, the DMG on page 4 says that the item's 3.5 legal but is nonetheless subject to what it calls "minor adjustments" by the DM. Again, ask the DM. Finally, bear in mind what an attack roll means.)
This makes the crescent knife—sort of, in a way, from a distance in poor light, if you tilt your head and squint, just maybe—a light double weapon, except for, well, a lot of exceptions. But, if the DM agrees, a Medium creature may be able to wield two crescent blades each designed for a Large creature 1-handed with a −2 penalty on attack rolls for inappropriate size (and, obviously, standard penalties for two-weapon fighting), which might be close enough visually.
As one of the few exotic weapons that's actually worth the Exotic Weapon Proficiency feat, some care should be exercised in introducing the weapon into the campaign.