The bare minimum would be something like this:
Sensor power and the pull-up are both controlled by a single PFET. In this design, you could actually skip the PFET and power it directly from a Pi pin, but not preferred. However, this runs the sensor at 3.3V, and some of the cheap sensors really run better at 5V... so this is the bells and whistles version:
In this case, a high signal on the Pi Pin will turn on the sensor, and pull-up the 1-wire line via R1.
R2 is to pull the PFET gate up to 5V, which will keep it switched off unless Q2 is turned on. When Q2 is turned on by the high signal from the Pi, the gate of Q1 goes low so it turns on, and R2 limits current to ground.
R3 and C1 are the extra bonus parts - R3 will make sure any charge is bled away from the sensor (it may latch in a very low current state and may take awhile to reset), and C1 is good practice to decouple the power line.
1Wire sensors can be powered parasitically, so it may be valuable to add a large value (100k+) pull-down on the 1Wire bus line at all times. In theory you could do so by simply setting the 1Wire pin as a low output on the Pi, but the kernel driver owns the pin so its not straight forward.