what exactly do you mean, armor, weapon or jewelry glyph? and a glyph that just adds max magicka?

all i can give you for information atm is:
when you cyrodill, southern gate their should be a house with an enchanting table, the guy sells glyphs for alliance points (very cheap don't worry), but useally you ask people to craft you those glyphs, or you buy them from players, or make them yourself

You can't buy this Glyph you would need the negative potency for your level, a Makko essence rune and the Aspect rune of your choice. All can be acquired by purchasing negative Glyph from low level area extracting them for the Potency Stone and Essence Stone. Buy magicka glyphs low level and extract for the essence runes Makko then Aspect runes come from hireling or surveys or node farming

Or if you're on xbox one EU I could help.

Hope this helps.