If you would like the DS4 in a yoke configuration, simply specify that to the Apeks/Aqualung dealer when placing the order. The dealer should be able to sell a yoke-configured DS4 with any of the Apeks second stages (XTX200/100/50/40/20). As eelpout pointed out, Apeks/Aqualung first stages are typically paired with certain second stages for convenience and/or marketing reasons, but they are all meant to be interchangeable. Any dive shop worth it's salt should be able to accommodate your straightforward request. I obtained both DIN and yoke parts for my Apeks first stage. The yoke parts are stashed in my dive closet at home most of the time. I'll only convert from DIN to yoke when I go on a dive vacation where I know I'll be encountering primarily yoke tank valves.
FYI, the Apeks DS4, DST, FST, and FSR first stages all use the same yoke clamp [AP1403], yoke clamp connector [AP1407], and yoke clamp screw [AP1402]. For cosmetic reasons, the yoke clamp comes in a "satin" or "chrome" finish to match the rest of the first stage.
For what it's worth, I have used a DIN-configured Apeks first stage (FST) with a spin-on DIN-to-yoke adapter on many occasions and have never had any issues with the first stage protruding too much. At least that's been my experience.
Good luck with your reg purchase...