I found this video showing a the electroless nickel plating:

He is using a chemical solution from janekits in Australia, but seems like their website seen to not respond anymore.

Then I asked Google for a proper formula to these chemicals and here we go:

The basic chemical formula for an electroless nickel plating solution is based on an autocatalytic (electricity-free) redox (reduction-oxidation) reaction. Unlike conventional electroplating, this process requires specific chemical compounds to reduce nickel ions directly onto the surface of the workpiece.

A standard formulation, widely used in the industry and in technical manuals for metal finishing, consists of the following ingredients per liter of distilled water:

Classic Electroless Nickel Formula (Phosphorus-based)

• Nickel Source: Nickel Chloride (NiCl₂ ⋅ 6H₂O) — 20 to 30 g/L (or Nickel Sulfate — NiSO₄).
• Reducing Agent: Sodium Hypophosphite (NaH₂PO₂) — 20 to 30 g/L (provides the electrons necessary for nickel deposition).
• Complexing Agent / Buffer: Sodium Acetate or Malic/Lactic Acid — 10 to 20 g/L (prevents rapid nickel precipitation and maintains a stable pH).
• Stabilizers / Brighteners: Trace amounts (milligrams per liter) of compounds such as bismuth sulfate or thiourea (prevent the bath from collapsing or reacting spontaneously throughout the entire tank).

Operating Conditions

For this formula to function, the bath cannot operate at room temperature. It must be heated and strictly monitored:

• Temperature: Between 80 °C and 90 °C.
• Ideal pH: Generally maintained between 4.5 and 5.0 (acidic range). Commercial concentrates sold by companies like Jane Kits already contain these compounds, perfectly balanced and stabilized to prevent the solution from spoiling quickly.

More info: https://chiggofactory.com/a-detailed-guide-to-electroless-nickel-plating/