How do you make custom letters or glyphs in photoshop and/or illustrator?

Hello, I'm trying to make a border pattern along a circle(in photoshop) and it would be a lot easier if I could use the type-on-a-path tool to keep everything evenly spaced but I can't find any way to make custom letters or glyphs in photoshop (or illustrator if I have to) without the use of an unrelated software. 

Is there any way to make custom fonts or add custom glyphs in photoshop and/or illustrator? I've tried everything and looked around and I would rather not have to download another software for this. Please tell me any solutions you have for this type of process. [and adobe if you're listening please let us make custom fonts and glyphs in the future! :c]