comments:
Buy the cheapest one you can find on Amazon that explicitly mentions "FT245". Like this one. Reason: the even cheaper ones as using a microcontroller to drive the JTAG pins and they will notoriously mess up the signal timing, going way faster than the 6MHz that is the limit of regular USB blasters. When there's an FT245 chip, the pin timing is hardware, not software, controlled, and consistent.
They often don't work. One reason they don't work is because they often have incorrect bit timings. E.g. the JTAG clock might toggle at 20MHz even when the official one doesn't go above 6MHz. There are tons of implementations, with entirely different chips under the hood, even if the case is the same, so you just don't know. My advice is to find one on Amazon that explicitly lists "FT245" in the product descriptions, like this one. The official USB Blaster also uses an FT245 and they have consistent bit timing.