RegEx to add a space after a comma

There is a similar question about this topic (here), but I added a question at the end of it that's never been answered - possibly because the original question has already been marked as solved.

I use @burked's solution for getting rid of the brackets and quotation marks from items in a collection, and that works fine. But it seems that NWC no longer puts a space after the comma that separates the items. So I get output like this:

Choice 1,Choice 2,Choice 3,Choice 4

Of course, what I want is this:

Choice 1, Choice 2, Choice 3, Choice 4

I know next to zilch about RegEx, so I can't figure this out. Is there an expression to add a space after each comma so that the output isn't so ugly?