The metal parts are either readily available or can be made but if you want to buy a kit with all the metal parts ready to go we have you covered:
We have put together all the metal parts needed to make your own router plane. The parts are high quality off the shelf parts in the case of the washers, bolts, and nuts. In the case of the retainer bar and blade those are both made here in the UK by trusted manufacturers to a high standard. The blade is made from O1 tool steel and hardened, tempered, and ground to a 25-degree angle. You just need to hone the edge and it is ready to use in your router plane.