Hi,
Due to constant back pains I made myself a backrest for my drum throne the other day. One of our kitchen chairs collapsed and I decided to recycle it.
Here's what it looked like before cutting it:
I unscrewed the metal bracket the shaft of the stool base inserts into and screwed it onto the chair.
After cutting it, I screwed on the top half of the backrest to the bottom half as it was a bit too far back. Padding was added later for comfort and to get it closer for better support:
Here it is finished. Sorry, but I don't have any pics of the padding - I used some insulation material that is quite firm and that I had left over from making a platform for the e-kit. Did some testing to get the thickness, height and distance right for good comfort as it is not adjustable later. I then covered it all with part of an old handbag that the missus had at home and which was a perfect fit:
Does the job great and at zero cost. The chair is from Ikea and the seat part (without legs) can be bought for around 12 euros.