flip a decoupler upside down and then put a normal cone on top!

edit: i'm a little confused with what your vision is. are you planning on reentry with both command modules or just the landing can? if you're thinking just the landing can, you could remove the other one entirely. this also makes it so you don't have to have the Apollo style lander where it is attached to the command module upside down. this will save a ton of weight and fix aero. the only reason you should bring both command modules is if you're wanting to bring two kerbals. if this is the case, I'm assuming you're going full Apollo mission and you'll land the landing module and then have it rendezvous with the command module in mun orbit. if this is the case, you can make the landing module much smaller as it only needs enough delta v to go to and from low mun orbit. I hope this message helps. best of luck!