But this essentially boils down to "play more"; mom's eye isn't a shop item (or is it? if it is I haven't ever seen it) so it's just a case of finding it. The rest of mom's items are pretty common so they're not an issue.
I would recommend doing Isaac playthroughs to help get the remainder of the items you don't have. Being able to reroll item drops is pretty helpful for that purpose.
I've seen mom's eye in the shops. Pretty sure anything can be in the shop except satan room items and the 1up (?)
Certain items are exclusive to the secret room. The 1-up, noose, liver, etc are from that list of 6 or so items that can appear there. I know that the unicorn horn isn't exclusive, but it can show up in there.
Edited:
5th run, i kill mom and have awesome gear, satans room opens brings me to sheol (how the fuck is this even possible),I go to hell and come to satan and get killed on his 3rd form on 10% hp ALL MY RAGE
The devil room can appear in the womb 2 just like with any other floor. Instead you are sent to Sheol instead of making a deal. It's how I unlocked the Monster Manual before I unlocked Blue Baby