I've used the NECG safeties, quality is tops. They're not inexpensive.

Gentry in Montana makes one http://www.gentrycustom.com/ He's removed pricing info from the website. Before the father died and the son took over, a year or two ago, the price was $150. I have one of their safeties and the quality is very good.

Brownells and Midway both sell the safetys also, made by NECG and Gentry.

dave