Where did the cliche come from of wizards wearing robes festooned with stars and planets? Did any real-life self-styled wizards ever dress this way?
I’m betting it was more of an illustrative association than literally on clothing, but most historical magicians were also/instead what we would think of as astrologers, so would be concerned directly with the objects of the heavens.
For another association, alchemy was another career path that we would consider magical/wizardry, and a lot of alchemical symbolism was wrapped up in precious metals and in the representation of various aspects of the sun, moon, and stars.
Since you’re looking for a factual answer, there are no real-life wizards.
That’s not an answer to the question the OP asked. 
The wizard (that Mickey Mouse was apprenticed to )in “Fantasia” by Walt Disney wore such a robe.
Is there any evidence of Medieval bedazzlers?
A picture of Merlin the Magician circa 1300. The robe style might be associated with Druids or Catholic clergy. I’d wager the sparkles are a theatrical creation.
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Um, that’s a picture of a painting of Merlin. It’s not a photograph of Merlin. And I thought the Arthurian tales were from around 1000, not 1300.
Yes. Let me be clear. It is not a photograph taken of Merlin the Magician in the year 1300. It is an illustration, made around the year 1300. Probably not based on actual pictures of Merlin either. Do I have to explain why?
He’s a wizard, and can make the camera not work?
That’s ridiculous.
Clearly he was a vampire.
…that doesn’t mean The Once and Future King or The Sword in the Stone are from around 1000. If there’s an example of an epic cycle that’s been rehashed time and again, it’s Arthur’s.
But the pic shows that back in 1300 people (at least, that individual artist) didn’t feel the need to put rhinestones and glitter all over a magician’s robes in order to spell out m a g i c i a n.
I beg your pardon, there most certainly are real life wizards. And yes, some of them do wear “spangled” wizard robes, at least for photo ops (and, okay, I’ve seen him wear it just hanging out, too.)
So, somewhere between 1300 and today is where we can narrow it down to.
To counter-quibble the quibble raised above, the word “picture” does not necessarily imply photography. The Surveyor of the Queen’s Pictures does not just keep an eye on photos.
Was it not clear that the OP realises this? (the term ‘self-styled’ in both title and post)
You might like to tell that to the Official Wizard of New Zealand. But he doesn’t have spangled robes.