Thus far...I really like the iXpand USB Flash Drive from SanDisk. I have a 256GB and just plug it in to my iPhone to view contents. It has an app that allows you to view the clips (as otherwise the IPhone can be a bit challenging in getting things plugged in to it and recognized).
Also like is the SentryView app as a companion to this-as it allows you to multiple views (cams) simultaneous and you can speed through them or slow as you choose.
I've had really good luck with this Samsung USB Flash Drive. It's $23 for 128 GB and will store lots of Sentry/TeslaCam videos as well as provide extra space for music files if you create another FAT32 partition.
If you want the absolute best in reliability, there is a better option though, and this is what I now use for my TeslaCam/Sentry drive.
First you need this Micro SDHC card. It is made by Samsung and part of their Endurance lineup that is specifically designed for video monitoring camera applications such as TeslaCam/Sentry. It is specially made for continuous recording applications with transfer speeds up to 100MB/s. It's more expensive but IMHO worth it.
Next you need the following adapter so you can insert the SDHC card into the adapter and then plug it into your computer to format (FAT32 partition) and then you can insert the adapter with the SDHC card into the USB port of your car. Of all the adapters I have tried, I like this the best because it is tiny.
I was using a small USB drive, barely bigger than the USB port, hardly stuck out. Was made by sandisk I think. Lots of corrupted empty files. Sometimes it worked, sometimes it did not. Was certain it was a problem with the Tesla software. It was only 32GB and filling up quickly.
I decided I wanted something bigger and then went to a raspberry pi with a 64 GB micro sandisk card(sandisk endurance), running teslaUSB. I stopped getting the 0 length files, but Tesla would cut the power to the USB ports at bad times, throwing off the operation/reliability.
The I switched to a mini USB reader that holds the 64 GB micro SD card. That works much better. No issues, except sometimes the clip will start out green.