Thank you for the support and advice. So, I'm proceeding with the modification. I've just ordered a 0.5-liter membrane accumulator, which is approximately 17.59754 UK fluid ounces for the English-speaking audience. The cost is not insignificant, at 100 euros. If it arrives next week, I'll have it charged to a pressure of 18 bar, 261 psi at home.I've cut the sphere and used a cardboard template to take measurements for the steel plate to be welded. As you can see in the photo, the membrane is torn at the edges where it's crimped due to significant stress over 24 years, causing nitrogen leaks.Of course, all of this will be done in my spare time outside of work. I'm not a mechanic, but I'm a computer scientist with a passion for mechanics. I have a well-equipped garage for mechanical work. I'll update you soon on the progress of the project.Best regards,K