@Pepeps thanks for reaching out, what a great idea for a way to keep reusing your sleeping bag! Unfortunately, we aren't aware of a shop that does this kind of work specifically. You might call Rainy Pass, which is a Seattle-based shop that specializes in gear repair and alteration. You could also  check with a local tailor/seamstress shop in  your area (although you'd want someone who knows about feathers and technical fabric! We'll also move this post off the "Ask an REI Employee" board to see if other community members have ideas/suggestions! @OldGuyot @Philreedshikes @Rob6 @hikermor - any thoughts?!

We removed your second post as it contained personal contact information, to help protect your privacy.

@Pepeps Back in the day, my mom, an accomplished hobbyist seamstress, made several down-filled clothing items for us from kits made by a now defunct company called Frostline, and she would patch, repair, and modify when necessary.  I can tell you from my memories that working with loose down is a challenge at best!  Not for the faint-of-heart.  

If you are looking for local places, I would Google search for seamstresses or an alterations place, as suggested by @OldGuyot .  One other idea that came to mind is Patagonia's Worn Wear program.  They may be able to help.  https://wornwear.patagonia.com/

This is a great idea.  Good luck!

@REI-JenK  @Rob6  Thank you all so much. I did find a person who does this work and will have the foot opened to metamorphose it into a flat though oddly shaped blanket.  
I will try to take before and after photos to include in a follow–up report. 
Thanks again!

Pepe

@Pepeps please do! We'd love to see how this turns out!

@Pepeps If you know what you want done,  ask your local alterations places.  Often they have the skills an may be glad of a more interesting project.  Probably won't be "economic" though. 

@Pepeps As stated, might not be worth the cost.  Sometimes I use a sleeping bag as a blanket bu simply unzipping it and crawling under.  The foot section remains as a closed pocket, but that often works out quite well, and the price is right!

I recommend using it as a 2 or 3 season quilt.  The bottom down of the bag is useless anyway, your bottom insulation is from your mat.

It's best used as a quilt if there are no inside baffles which would prevent you from evenly shaking the down between the top and bottom.

Bear in mind, that if you able to distribute the down evenly between top and bottom, that decreases the top loft by about 1/2 so your cold rating goes from about, for example, a 20F bag to a 40-50F bag.

I find quilts are SO much easier to turn over in anyway.

good luck

@Philreedshikes Here’s some follow up. I went to an alterations seamstress who opened the foot and left the zipper in place. This is also good as the sleeping bag function remains, though perhaps diminished lightly. The foot of my new comforter is a bit narrower than the top, and this may be a minor detraction.  She charged me $40.  
Here are some before and after pics. (Sorry, photos not uploading, but you get the picture!)
Thank you all for your friendly help!

Pepe

Another thought, especially if the bag is old, torn, patched, etc. or tapered and looks odd, would be to put it inside a duvet cover. IKEA sells them for as little as $13, e.g. TRÄDKRASSULA.