Box, have a look at these.
Revolution Racegear
The problem however, is that they are FIA tagged but not ADR tagged.
According to Revolution, this isn't a problem as most engineers have an approval chart for FIA conversion to ADR's and that heaps of folks have fitted them with engineer approval.
This seat also requires a 5mm alloy plate base between the seat and the runner/fixing to the car to be ADR compliant.
Check with your engineer I spose.