Wedge Engineering makes the brackets for 90% of seat manufacturers in the US. If you order Sparco brackets, they come from Wedge Engineering. If you order Konig brackets, they come from Wedge Engineering. If you order Nopi brackets, they come from Wedge Engineering. See a trend yet?

Unfortunately, that may be your only solution, besides having the ones you have customized by somewhere like Batlground or Mainstream.