Just hopping in here really quick.
I have been using DDC pumps for probably over 15 years now in water cooling builds. Never once, and I mean NEVER have I ever needed a heat sink on the pump. 2 of the original three pumps I have are still in operation and have been in many builds. Only one pump has failed and it was no fault of its own, it was my fault in a physical damage situation. The idea of those pumps requiring a heat sink is ludicrous. The pumps do run a bit hotter than some other pumps, but its by design and does not effect the performance.
With that said, there are heat sinks out there for these pumps, and honestly its about style. Not functionality. If anyone ever tells you that your DDC pump requires a heatsink, roll your eyes and walk away.