General Knoppix support for those who've read the FAQ at the Wiki
Fortinet Fortiwifi 60D FG-60D Security Appliance Firewall / VPN w/ AC Adapter
$34.97
CISCO ASA5505-BUN-K9 SECURITY FIREWALL UPGRADE ASA5505
$44.99
Sealed AlphaShield Personal Hardware Network Firewall Panda Platinum Security
$27.00
Ubiquiti Networks USG Unifi Security Gateway Router/Firewall ** FAST Shipping **
$46.99
Palo Alto PA-220 Next-Gen Firewall 750-000128-00A w/ Power adapter
$68.00
Netgate SG-3100 pfSense Security Gateway Firewall Appliance w/Power Adapter 32GB
$150.00
Protectli The Vault 4-Port Firewall Network Appliance FW108120 51524F17
$149.95
PFSense Netgate SG-2220 Security Gateway Firewall Appliance As Is
$60.00
Check Point 1450 Network Security/Firewall Appliance CPAP-SG1450-NGTP
$60.00
OpnSense PFSense Firewall - Enhanced Cooling - N100 - 2.5 Gbe 6-port - US Seller
$330.00