I haven't seen this yet on the postings. I have a weight that fits on my shoulders/back with straps that fit over my arms. It causes me to sit straighter instead of hunching over, making my shoulders and back feel better.
I don't see why you couldn't make one like a rice microwave bag with elastic attached to fit over your shoulders. The one I have costs about $50-60, and you see it for sale in quilting book ads. Much more economical to make one. I also have a cutting table that folds down to about 12" if you need more room. I live it up and ready to cut on most of the time.
Chiropractors are also helpful, but you can't have one "in" your sewing room unless you have one for a DH/DW or BF/GF! I see mine weekly.