Does anyone know where to find this tool?

[mvptrukin]

^^This.^^

You can get any style female sliding sleeve coupler to grab on to a valve stem but that's not what they are designed for. I rather spend a few $ and get a more secure connection because I usually use a bead blaster that will easily dislodge the regular couplers. I use one like the member linked in post #15 and have a re-capper coupler like the one the OP was looking for but in "T" style. Also, I have one like in this link that is now my go to:
http://www.toolsource.com/advanced_search_result.php?search=1&query=milton+S-696&x=24&y=16

 

[a40lover]

I've only seen them in Tru Flate style, they call it a retreaders fitting. NAPA sells them.

 

[Octavioramos]

I am just now seeing this thread but yes I had the same fitting and lost it, but I found it again!!! MILTON 731 I wouldn't recommend it on cars or smaller tires but it works awesome on semi tires I just ordered 20 of them for 31$ shipped to give out to my trucker friends

 

[gungatim]

If you have type M couplers, just push the coupler down over the valve stem (w/o valve core). The valve stem will open the valve in the coupler, and the valve stem rubber body will seal against the metal body of the coupler.

I can't believe nobody suggested that already. It works great for seating beads.

ditto. have done this many times. have even inflated tires with the core still in the stem that way when putting bikes together for a Christmas give away and they didn't have enough chucks...

rubber tipped blow gun with the restrictor removed also works...