multiplexer with floating outputs
You could use a 74HCT138 and drive a ULN2803 transistor array from its outputs.

The 74HCT138 is a 3-to-8 decoder. All outputs are driven high except the code-selected output which is driven low.

The ULN2803 contains 8 Darlington transistor drivers with input base resistors and open-collector outputs. A logic high input drives the output to 0.8..1 V. A logic low input lets the output float at high impedance.

If the ULN2803 'on' voltage is too high for your application, you could look for a FET equivalent or consider using discrete logic-level N-channel MOSFETs.