How to get a glowing Tamagotchi in US?

I don't know how Japanese people get Glowing Tamas. Any tips?

 Can you specify what tamagotchi you are referring to?

There is a Connection Version 4 glow in the dark tamagotchi it look like this:



There are plenty of people that make custom shells including glowing paints, I requested one two years ago for my Entama from a trusted tamagotchi surgeon. This is what it looks like:




 

This is her instagram account @tamagirl327 you can check her awesome work!  

I think OP is referring to the coloured outlines that the Pastel Meets and Fantasy Meets / Wonder Garden ON have which also seem to make the Tamas look like they're glowing. Unfortunately, as far as I know, these can only be obtained on these versions, and cannot be inherited on other versions 

https://tamagotchi.fandom.com/wiki/Color_Genetics_and_Combinations#Color_Outline

 What if there was a Purple Outline for Magic?

There won’t be unless you have Pastel Meets/Fantasy Meets/Wonder Garden.

I have a Pastel Meets and the special, light blue outline is actually gained by using the Easter egg the tamagotchi receives upon visiting Easter Land. This allows any character at any stage to not only have their outlines turned blue, but also take on a completely pastel colour scheme (and also reverse the change). The colour scheme differences are very distinct as the Easter egg can change green into mint and dark blue into light blue (those are the two I remember). It's a nice feature since if you wanted to easily change your tamas colour a bit, you just need to select the item. Unless a particular colour model has specific characters with non-black outlines, the option to change outlines probably doesn't exist.