U2Fzero - FIDO U2F USB token

• Available for about $8 from Amazon
• Microcontroller - 8-bit Silicon Labs chip with 16K Flash
• Secure Element - Atmel's authentication chip - one of the simplest and cheapest SE elements possible
• Open Sourced hardware and software
• CONS - same token can only be used on less than 16 websites b/c Secure Element chip can only hold up to 16 ECC Keys. This might be fixed with newer firmware versions though but it would require a major change in the key management strategy - from storing up to 16 ECC keys (existing approach) to deterministically generating unlimited number of ECC keys on the fly, without storing them in the SE chip (new approach)
• https://u2fzero.com/
• https://github.com/conorpp/u2f-zero

Nitrokey - USB FIDO token plus More

• 9 to 199 EUR - different models are available from 9 EUR (for simple FIDO U2F token) to 199 EUR (for USB token with advanced functions like encrypted storage etc)
• https://www.nitrokey.com/
• Microcontroller - STM32 F1 series
• Secure Element - some models do NOT have SE at all, some models use external SE in a form of pluggable Smart Card (small form factor like SIM card)

CrypTech Alpha - Open Source HSM

• sells for $800 USD
• https://www.crowdsupply.com/cryptech/open-hardware-security-module
• https://cryptech.is/
• combination of STM32 F4 and FPGA. Crypto is done in FPGA

USB Armory - secure ARM Linux computer in a USB form factor

• sells for $130 USD
• https://www.crowdsupply.com/inverse-path/usb-armory
• http://inversepath.com/usbarmory.html
• Freescale / NXP Cortex A CPU, 512 Mb RAM, SD Card

These cowdfunded projects are interesting but NOT yet shipping:

Signet by Nth Dimension An all-in-one encrypted USB flash drive, two-factor authentication token, and password manager

https://www.crowdsupply.com/nth-dimension/signet-high-capacity