I had a 3rd party buttstock on my A-5 which broke and I had no idea where the original went and it will not function without one. My design attaches with 2 zip-ties but I can attest that it works great. I recommend printing this in ABS/ASA or a good PLA+ with high infill.
I have included the FreeCAD save if you want to modify/improve it. It's a bit ghetto since I had very little CAD experience at the time. If you can decipher it, more power to you.
The author marked this model as their own original creation.