It seem that every shop only stocks enchanted robes .

Radient Raiments in Solitude sells "College Robes", and the masters at the College of Winterhold occasionally have a "Mage Hood". Both are unenchanted. You'll likely have to try a few times to get the Mage Hood in stock, but it's there.

Those College Robes and Mage Hood have the same appearance as Novice Robes and Hood.
Do Radient Raiments also sell the ones that have the same appearance as Expert or Adept Robes?

I just want my clothing to reflect my academic degree .

Yes they are Novice Robes in appearance. As far as we know there are no unenchanted Apprentice, Adept, Expert, or Master robes/hoods in the game. If you are on PC they will be modded in after the release of the Construction Kit in January, otherwise you're stuck with Novice.

Guess I'll have to live with looking like a novice forever then. Ohh,.. this doesn't help at all with those town guards who always belittle me.

There is DEFINITELY an expert robe that I've found in Radient Raiments that is unenchanted

I can 100% confirm that. No idea if it's randomly spawning or anything though