I don't think it really has a name. It's still an IDE connector, but when Ultra-ATA/66 came along it changed the cable to the 80-wire cable, and that's when the blocked pin really came along (and also the blue/grey/black color coding)
Also note that while the Ultra ATA/66 specifications calls for a 80 pin IDE cable, only 40 pins are actually used for data and control signals, the second set of 40 pins are paired with the originals and act as ground wires.
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While the pin designations remain the same as with regular IDE cables, at Ultra ATA/66 speeds signal quality issues become a major concern. It is due to this fact that your system needs to determine if you are using the newer 80-pin cable, or older 40-pin cable, before it will enable Ultra ATA/66 mode. While the pin designations are the same, as stated above, one of the lines is broken, where in the 40-pin cable, the connection is unbroken. It is this broken connection that the system will pick up on, to determine if you are using the correct 80-pin cable needed for Ultra ATA/66 operation.
So you're still looking for an IDE Cable, but I don't think there's a good name for a "Pre-Ultra-ATA/66 40 wire IDE cable", and almost all of the cables you will find new will be the newer cables since that's been the standard for over 20 years.
You're looking for a cable that has 40 wires, like this, and I think you'll just have to keep searching for IDE cables until you find one:
