I do not believe the original poster is talking about the Delta Dart - either Cold Steels plastic version, or the original Steel version by Pat Crawford, called the Devil Dart.
I think what MichaelOsborne is talking about is this:
A WWII vintage OSS/SOE type spike, with a triangular blade and rectangular handle.
No one makes a "good" 100% reproduction of any of the OSS/SOE tools these days, but this tool, rendered in 420J2 by Chinese manufacturers, is commonly sold by places like Bud K, sometimes as a thrower. Its 420J2, but that wont matter as it doesnt really have an edge, its a stabbing tool - for its intended purpose, the 420J2 version would work as good as the original I posted a pic of.
I believe H.G. Long reproduced, with high quality, many of the original WW-II OSS/SOE clandestine/covert blades and spikes, but they are no longer doing so - and their stuff is about as hard to find as originals.
There are a few makers who do things like this, Bill Siegle makes some thumb daggers occasionally, he has (or had last time I Looked) one for sale in the Makers for Sale forum here on BF.
Fred Perrin makes a variety of blades that qualify as this sort of thing, from La Griffe versions to spike sof various kinds and sorts.
Of course, Pat Crawford makes the steel Devils Dart and a couple other weapons of this type.
Besides myself (I have a penchant for spikes and small concealable blades, modern variations [non-metallic, modern materials and whatnot] on the old concepts, so I make 'em a lot, just for fun) those are the only ones I can think of.
Actually, there is one other -
ShivWorks and Trace Rinaldi make what they call the Lil' Loco that is designed, and implemented, just like an OSS/SOE piece might be, just in this case the designer/first user is a narcotics agent.
Don Rearic's Excellent Article on Covert Edged Weapons
Crawford Covert Knives
Small Knives, Theory and Application - An Undercover Agents Hideout Knives
The Lil' Loco
Rearics Article on Fred Perrin[url=www.szaboinc.com] Laci Szabo/Szabo Inc. carries several of Freds knives, and some others that may fit the covert description - be sure to look at the "hair pins" in Accessories.
An online catalog of some of Fred Perrin's wonderful little nasties, blades, push pics, stylets, etc. etc.
Have fun - these are wonderful little tools - addictive to study, and make.

And they could come in quite useful in the right situation.