Custom DC-Controlled Electromagnets updated -- 2

I need three compact electromagnets fabricated for integration into a larger prototype. Final outside dimensions will be supplied once we begin, but each unit must:
see diagram attached
• Run from a standard low-voltage DC source (anywhere in the 12–24 V range is acceptable).
• Provide variable holding force up to 40 N, adjustable via a simple in-line control such as PWM, current-limit circuit, or potentiometer.
• Remain within the specified footprint and include straightforward mounting points so I can drop them straight into my assembly.
• Operate continuously without excessive heat build-up or noticeable magnetic drift.
the electromagnets cores are close to 1-3 width, 100mm height and 10mm depth. they need to fit within a arm (harness) .
two magnets are curved and one is straight (going through the middle of a sphere)

Deliverables
• 3 fully wound and assembled electromagnets built to the agreed dimensions
• Matching driver or control interface with wiring diagram and basic operating instructions
• Short test report showing measured pull force at minimum, mid-range, and maximum settings
• Source files (coil data, CAD, circuit schematic) so I can reproduce or modify the design in future

I’m flexible on core material, winding technique, and exact control method provided the 40 N ceiling and size constraints are met. Please allow for reasonable shipping time and let me know if you foresee any alternative approaches that would simplify production or improve reliability.