As notquitethere posted, Dollar Shave Club x4 blades will work on the ATX if you pop off the adapter and insert the ATX adapter.
If you want to get the cartridges for even cheaper than what Dollar Shave Club sells them for, buy them from Dorco. Dorco makes the handles and cartridges for Dollar Shave Club (DSC x4 = Dorco Pace 4). All DSC does is repack and name them. Same for HeadBlade. The Cartridges are identical. HB4 = Pace 4, HB6 = Pace 6.
If you purchase from Dorco, use the following link for 20% off. http://dorcousa.refr.cc/L4H6KDJ
I just used it the other day and got a Pace 4 handle (comes with 2 blades) and a 24 pack of Pace 4 blades for under $27 shipped. Just over $1 per blade and I can use the same blades on my face and touch up around my head. Exactly what I was looking for since I recently started using HeadBlade ATX (which is awesome).
Nice site you have here. I found the Dorco deal and notquitethere's post from a Google search and figured I'd register and pass the deal on to my bald brothers.