CDI Presision has had them for awhile. I just looked at SSS kit, it looks good but I like the CDI better for the length of the mag release. One of these kits will be on my list for the next mod. CDI as far as I know is the only long action DBM and it looks like it will do WSM size cases which is what I need.
Try calling Lisa at SSS early in the morning and keep calling, I have yet to have to try more than three times, I have found SSS great to do business with!
CDI Precision Gunworks - CDIPrecision Gunworks