Reef Dynamics, formerly known as Euro Reef, may be out of business, but Titan Aquatic has you covered. A new website they just launched called Aquarium Source is slated to be the go-to place for all your replacement parts needs.
Reef Dynamics and Euro Reef protein skimmer famously stuck with modified Eheim pumps which use a very specialized needle-wheel impeller assembly to get the job done. The ceramic shaft in particular can be prone to cracking or outright breaking, and this part is not readily available from any source of Eheim parts.
This is where Aquarium Source comes in, with full replacement pumps and replacement impellers ready to keep your classic Euro Reef or Reef Dynamics protein skimmer alive and churning. Aquarium Source also is currently selling off some leftover inventory of the classic brand which include the recirculating Biopellet Reactors and In-Sump protein skimmers. [Aquarium Source]