bMobile and econnect Japan seem to be the only ones that offer data only sims for tourists.

They both state that a device that supports HSPA 2100mhz is required, however even if your phone meets that requirement but is not on their "compatibility list" they do not guarantee it will work so it's sort of a do at your own risk kind of situation. It's also kind of strange that aside from Nexus and Apple devices, a lot of flagship devices from Samsung, HTC, and LG are not included in their compatibility lists.