You had me at "flask."
I'm pleased as punch you decided to abandon your search for a bright fuchsia clutch. This fabulous DvF dress already has built-in color with the satin sash -- let that be the sole focus. Any more of a color burst, especially with an almost-kinda-sorta-the-same pink purse, and you run the risk of looking like a bridesmaid who had no choice but to wear the 13 pieces of clothing and accessories a misguided bride on an everything-must-match mission picked out for her and the other nine of her closest girlfriends.
Were I you, I'd opt for a textured black clutch, something in a brocade or embossed animal skin - animal skin, not animal print - that adds dimension to the ensemble without detracting from the primness of the dress and peeptoes. As for jewellery, even though you didn't ask, I would suggest minimal neutral studs (e.g. pearls, diamonds or opals) and an fun cocktail ring like this or even better, this. A thin gold necklace that hits just below the base of the throat would still look okay, but as you know, I always advocate erring on the side of simplicity, especially when the neckline, like this one, is an eye-catching accessory in itself.
Here are your flask-ready clutches, a couple of which, I realize, are pushing well beyond even an If-I-had-a-Sugar-Daddy price point:
Joan woven silk clutch by Franchi ($126.95 at zappos.com)*
Croc Lucia clutch by Lorelei ($198 at activeendeavors.com)
*my 'Since I don't (yet)' pick
**my 'If I had a Sugar Daddy' pick