There is something to be said for support for the CG Lock. I used to sell these by the hundreds and sometimes, you will want to go back to the supplier and replace a part. CG Lock is famous for their aftersales service, so pick someone that can help you.
Personally... and not everyone will agree, but I hope some do... I like supporting companies that support the forum. That would be Sector111 and BWR.
bwr's pricing is much better than s111's on this item. bwr offers a discount on multiples.
i would advise buying two if you have an instructor on the track... two reasons: some organizers mandate equal equipment both both driver and passenger, and this could be applicable to the CGlock, and also if it assists in any way to keep your passenger from sliding around in his/her seat and interfering with your driving then it's a huge safety/comfort addition.