Actually, BK adapters have been available for Colt Detective Special (Colt "D") frames (both long and short) since 2016. And customers have discovered that they also fit the Colt "E" frames, as well as the large frame New Service.
Several customers also have reported that the BK adapters designed for S&W K frames are a decent fit for the Ruger Redhawk. Another customer recently reported that those designed for the Colt Detective Special fit reasonably well on his the Ruger Service Six.
I have no Ruger double action revolvers, and so have not been able to confirm or test the fit that customers have reported. But their photos look like the fit is decent if not perfect. And they haven't sent any adapters back for a refund.
In the interest of full disclosure, let me offer one word of (temporary) caution: while I do work hard to get orders out the next working day (and sometimes they go out the same day as the order arrives) I am currently working full time doing tax returns for a local accounting firm. I will be done on April 15, but until then I will not have as much time available to make adapters. In addition, sales for the last 6 months are about 35% above the same period a year earlier, and the result is that I have been experiencing occasional outages of one particular adapter or another.
Right now I am out of black J adapters and only have 1 black K adapter left. I plan to make more of each tomorrow (Sunday) so that they will be available to ship on Monday if ordered, but they will not appear on the web site until they're actually made. Sorry, but it's just hard to keep up during this particular time of the year.