Topsi launches unlimited data (4G) in Taiwan this month, as low as $70 for the 5th day, $90 for the 8th day, $100 for the 10th day, and $160 for the 15th day. No matter how much you use, there is no speed limit.
There is also a 5G China data card, which only costs $32 after 2 days of 1.5GB speed limit. Japan and Korea as low as $88. All Topsi data cards can support wifi sharing (tethering)