For example, Wuerth WE-AFB LFS series model #7427727, alternating with WE-AFB series model #74270077. Those are for direct cable mounting, not clamp-on type (which are less effective and more expensive), so you have to remove the connector on one side of the cable.
These are high quality products and thus a bit costly but they are very effective... which often is not the case with any random far-east clamp-on ferrite you can buy on the usual platforms.
Together with Eupen ferrrite-loaded and shielded mains cable (e.g. Eupen GNLM 2.5, a bit hard to get, though) this as good as it ever gets, laboratory-grade EMC level.
Low Frequency Specialist | Core Material MnZn | Frequency Range 300 kHz to 30 MHz | Ø Cable 4.55 to 9.7 mm | Order Samples Free of Charge & Request Quotes Online | High Quality | Fast Delivery
www.we-online.com
Multi-purpose Bead | Core Material NiZn | Frequency Range 1 MHz to 1 GHz | Ø Cable 3.3 to 17.4 mm | Order Samples Free of Charge & Request Quotes Online | High Quality | Fast Delivery
www.we-online.com