I think I've found it!

I believe I have found my perfect carry-on bag. I'm not sure yet because I only just ordered it so I'm still waiting for it to arrive in the mail.
This is the "Charlie the Dino Print Daytime Tote" from the zh collection by Sanaa Hyder. I was able to snag one from Hautelook for $65 (50ish% off).

Sanaa Hyder designs these playful prints and combines them with sophisticated bag designs which ends up creating something chic and elegant but youthful and fun (at least in my opinion).

The dimensions (15" x 11.5" x 3.5") and shape are perfect to use as a carry on because I'm sure it'll slide comfortably underneath the seats on an airplane (or Amtrak train or coach bus). I like how it's tall because it's perfect for storing books and magazines (I always travel with something to read) and I think my iPad will sit comfortably in the bag. Plus, there are pockets on each side, one open (good for newspapers and boarding passes) and one zippered (good for feminine products).

They have so so so many cute things and so many cute prints. I also love how unique they look because you'll never have a hard time spotting your bag.
passport case
daytime tote

notebook handbag
carry on bag
reversible tote

I wish I didn't love shopping so much.

... Or I wish I was rich so I could indulge more often.