I picked up a 100 pack of "Amazon" spike darts from Jungle Blowguns on ebay. I paid about $16 shipped for them and they arrived very promptly.
The darts are 1" long pointys on a plastic cone and come "some assembly required" with the spikes and cones separate. I added a dab of superglue in the holes of the ones I assembled just to be on the safe side. The cones come off of my wire darts all the time and these seem like they'd be a bear to retrieve without a cone if they got stuck in something.
I've taken 20 or 30 shots and am very impressed so far. I really wanted to like these because I'm not really in to making darts. I like the way the premade ones fit just right and are all the same and I don't have the patience to make nail darts that way. Here's a video of them in action, they shoot good and hit hard. Diggin' em!