You could probably go with a Sedra KSP-5000 needle wheel pump, these are commonly used on Euro Reef skimmers and ASM skimmers, the Resun is a cheap knock-off of this pump. There's also the Gen-X line up which the essentially the same as the Sedra. You just have to be sure with either Sedra or Gen-X to get the new model which is smaller than the older model.
New:
Old:
Most retailers and online sellers do not list these pumps or stock them but they can usually order them in if requested.