I have one of these tiny inexpensive microscopes, and it is surprisingly good. But it didn't come with a clip to attach it to a phone camera, like this. It has a white LED and an ultraviolet LED so you can illuminate your specimen.
KingMas 60X Clip-On Microscope Magnifier with LED/UV Lights for Universal SmartPhones ($(removed)) on Amazon
Here's a video of a Russian guy unboxing it and trying it out: