GPS module with AHRS, barometric pressure and magnetic heading. $46 delivered
Case - buy two and attach them together to enclose the USB ports. (I ordered white to reduce heat while it is on the glare shield. The white reflects off the window so black might be a better option. Not really sure on this one.) $6 delivered
If you just want ADS-B weather receiver without GPS or the additional 1090 traffic receiver you can skip the GPS module and extra receiver. Total $94.48
Any 8GB or larger micro SD card will work if you already have one.
This is powered through any micro USB power supply. A car charger or auxiliary USB battery.