There are many 'ways' to soundproof a wall. On a recent Post, I put in this 'plug' for Owens-Corning Accoustical Batts. They, among others, may produce what you're looking for. DO realize that it's NOT an insulation material. (The 'paperwork' even on the WEB page says this.) Check w/other mfgrs. of insulation to see what they have. Since you're soundproofing an interior wall, keep your eye on the Ratings. (I don't know how to 'interpret' them ...)
My best to ya and hope this helps.
Jay J -Moderator
PS: You could do a WEB search on keywords to find more products. Use my link as a 'guide' for keywords ...