So you want a Stratum 1 NTP server...
Amazon.com: ICP DAS GPS-721 GPS Receiver and 1 DO, 1 PPS Output Module communicable Over RS-232 and RS-485. : Electronics
Creating an NTP Server Using GPS/PPS | ODROID Magazine
Using the Sure Electronics GPS evaluation board for NTP
Adding PPS to a cheap USB GPS stick | Brendan's Radio Blog
GPS-DO expansion board GPS input PPS and 10MHz output port USB PC | eBay
GPS time synchronization tutorial - Lammert Bies
Raspberry Pi GPS Module USB Port – Kuongshun Electronic Shop
An NTP Stratum-1 clock usng a GPS 18 LVC and FreeBSD
GR-701W 1 pps via USB G-Mouse Receiver (Important: European customers shall check new VAT rules before on-line orders as below) | Taiwantrade.com
Amazon.com: ICP DAS GPS-721 GPS Receiver and 1 DO, 1 PPS Output Module communicable Over RS-232 and RS-485. : Electronics
Adafruit Ultimate GPS with USB - 66 channel w/10 Hz updates - Boutique Semageek
Creating an NTP Server Using GPS/PPS | ODROID Magazine
Comint India | Products - Fullview
Millisecond accurate Chrony NTP with a USB GPS for $12 USD - Austin's Nerdy Things
USB GPS with PPS and pretty cheap too - Server operators - NTP Pool Project
VK 162 USB GPS Module GMOUSE /GPS Dongle G Mouse Navigation Engine Board Support RCmall FZ2421+FZ0576|Drone GPS| - AliExpress
PPS over USB
USB GPS Receiver Module GNSS GLONASS Antenna Laptop PC Tablet Car Navigation for Win7 Win8 Win10 XP G72|Drone GPS| - AliExpress
So you want a Stratum 1 NTP server...
z050 USB GPS Dongle with PPS - ZTI
Adding PPS to a cheap USB GPS stick | Brendan's Radio Blog
China Beitian USB Glonass GPS Receiver Gnss Receiver Nmea-0183 Flash Auto-Adapted Baud Rate Better Than Bu-353s4 Bn-81u - China GPS Receiver, USB GPS Receiver
Frontiers | Time Synchronization for Wireless Sensors Using Low-Cost GPS Module and Arduino | Built Environment
USB GPS GLONASS receiver dual GNSS receiver module antenna, New USB protocol 0183NMEA replace BU353,|gps glonass receiver|glonass receivergnss receiver - AliExpress
VFAN USB GPS Receiver | The Great Mojave Rover
