Attaching Temp Probe to Bucket

What does everybody use to attach their temperature probe to their bucket or carboy? I'm currently using duct tape over the bubble wrap which is over the probe. My problem is that the probe doesn't stay put. I'm using about 3 feet of duct tape and the probe stays in place for about 12 hours then the tape starts to fall off the bucket and the probe falls down. Anyone have any advice on how to do it better?

I cut a piece of insulating foam board. Hollowed out a channel on on side. Taped the foam to the side of my bucket with electrical tape. Slipped the probe in the channel between the foam and the side of the bucket. Works fine. I leave it attached like this for weeks at a time without anything falling off.

???? So are you mounting a probe on the outside of your fermenter in order to get the temperature inside it? How accurate is that? It seems like the plastic would provide a bit of an insulating layer, so your temps inside would always be higher, especially during the first 48 hours or so of fermentation...

Yep. Mounting on the outside. It's no less accurate than a fermometer strip. It's pretty close. I would suspect my technique is no less accurate than hanging the probe inside the bucket without submerging it in the liquid. If you want a more accurate reading, you can always buy a stopper thermowell and drill a bigger hole in your bucket lid. It will submerge your probe in the beer itself without getting the probe wet.