(I'm sorry this ended up being so long!

)
There is a student in my class who is a very reluctant writer. He always claims that he can't think of anything to write, gets a puzzled look on his face, and then just sits there.
In the beginning of the year, I noticed that his handwriting was very bad (I made a post asking for suggestions). He has been doing Handwriting Without Tears intervention for the past 8 weeks or so, and his handwriting has improved immensely! I thought that getting the handwriting under control may help his writing, but it has not.
Then I thought it may be a language processing/retrieval/memory issue, so I had him go through a speech and language evaluation. Everything came out fine on that end, too.
Some other things I have tried (that have all failed):
-Having him type a story. My class has a subscription to the website Wixie. All of the other students are highly motivated to use the site, but this student is not.
-Having him dictate a story, while another adult types.
-Having him speak into a microphone to record a story (students do this in Wixie, as well).
-He loves drawing, so I tried to get him to draw first, and then write about his drawings.
Because coming up with an idea for writing is half the struggle with kids this age, I have done a number of things throughout the year to help my students with this: ponder pockets, heart maps, lists of important people and places, sentence builders, story starters, etc. I also have a number of (usually) highly-motivating writing options for independent work on writing time: pictures of animals with writing prompts, silly story starters, creative thinking starters, cartoon story starters, comic strips, Draw then Write, etc. For a while I thought that maybe he had too many options, so I had him focus on one or two choices only, but that didn't work.
Whenever I do a writing project, I start with a graphic organizer. I walk students through it one step at a time. He can usually fill out the graphic organizer ok (it's a struggle, but it gets done). However, when it is time to put it together to make a story, he just copies his notes. He ends up with a story that is 4 sentences long. Whenever I prompt him to add details with sensory words (we have lists of sensory words), or onomatopoeia words (they have their own onomatopoeia dictionaries that we add to frequently), he says that he can't think of anything. Even when I pretty much tell him the words to write, he won't write.
With the story we most recently wrote, I had him work with the literacy specialist, because I am at a loss. SHE is at a loss, too, and doesn't have any suggestions for me.

She couldn't get him to write a darn thing, either!
What now?!! I feel like I am at the point where he is just being lazy and stubborn. He does not have any other behavior or academic concerns-just writing! I do not know what to do to motivate him. I'm to the point where I may just start punishing him. Maybe he has to stay in for part of recess every day until his story is written to meet 2nd grade standards. Or maybe I start giving him multiple choice options (characters are a, b, or c, setting is a, b, or c).