Looking interesting!
Since you're going to be without the 'distinctive' modelled parts of Harlequins that make them stand out (the masks, Harelquin's Kisses etc) I think the painting will need to make them stand out from the rest of your
DE's, interested if you've got a plan for that?
As for parts, I can think of a wrist-mounted shuri-pistol from the Dire Avenger sprue which might be convertible into a Kiss (
http://www.bitzbox.co.uk/product_info.php/eldar-dire-avengers-exarch-shuriken-pistol-arm-p-997), and as they give you more than you need in the
DA box if you know a Craftworld Eldar player they might have some spares.
Also, if you can grab one of the old guardian
CC weapon sprues, that should supply you with the pistols (Fusion pistols etc.) as well as some swords. (
http://www.ebay.co.uk/itm/Warhammer-40K-Eldar-Guardian-arms-weapons-plastic-/350509497366?pt=UK_Toys_Wargames_RL&hash=item519bfe7c16#ht_1052wt_1139)
The links are just for examples, I'm not trying to promote them specifically :-P