I don‘t have access o earth
if you take a ferric material and completely enclose your circuit, you will effectively shield your circuit from the magnetic field. some people will suggest a faraday cage, but that's only to stop alternating magnetic and electric fields.
All vacuum tube based high end stereo systems use shielding around certain tubes. The shielding is a simple steel or aluminum sleeve that fits around the tube and is grounded to the chassis by direct physical contact.
If you truely need MAGNETIC shielding only ferrous mateials will work. Electric fields (E-fields) can be stopped by other metals like aluminum, but magnetic fields (H-fields) are only stopped by iron. Not knowing the details of your circuit makes any further suggestion difficult. However, I can describe how H-fields are generated. Current flowing through a conductor creates an H-field around the conductor according to the right-hand rule. The larger the current, the larger the H-field. Any other conductor which happens to be in the vicinity of the H-field will have a current induced in it. That's how the noise propogates. You need iron or ferrite.
