Hardware write-protected USB flash drive for Tails OS

What capacity?

Tails OS needs >4 GB of space.

Hardware write-protected USB flash drive list

Currently (Feb 2017) we have this on the market:
  1. Netac U335 - 16 GB (minimum capacity) - $12.99. No BadUSB protection. Low price.
  2. Kanguru FlashBlu30 - 8 GB - $17.95. No BadUSB protection.
  3. Kanguru FlashTrust - 8 GB - $29.95. Protected from BadUSB.
  4. Kanguru SS3 - 16 GB (minimum capacity) - $39.95. No BadUSB protection. High price. Don't recommend.

Why not SD card?

It's not hardware write protected.

From the Wikipedia Entry on SD Flash Cards
The user can designate most full-size SD cards as read-only by use of a sliding tab that covers a notch in the card. The miniSD and microSD formats do not support a write protection notch. 
When looking at the SD card from the top, the right side (the side with the beveled corner) must be notched.
On the left side, there may be a write-protection notch. If the notch is omitted, the card can be read and written. If the card is notched, it is read-only. If the card has a notch and a sliding tab which covers the notch, the user can slide the tab upward (toward the contacts) to declare the card read/write, or downward to declare it read-only. The diagram to the right shows an orange sliding write-protect tab in both the unlocked and locked positions. 
The presence of a notch, and the presence and position of a tab, have no effect on the SD card's operation. A host device that supports write protection should refuse to write to an SD card that is designated read-only in this way. Some host devices do not support write protection, which is an optional feature of the SD specification. Drivers and devices that do obey a read-only indication may give the user a way to override it.
From the Wikipedia Entry for USB Flash Drives
In contrast to SD cards, write protection on USB flash drives (when available) is connected to the drive circuitry, and is handled by the drive itself instead of the host (on SD cards handling of the write-protection notch is optional).