Top Notch does the conversions ,but they are expensive . Ive seen a lot of these for sale where it looks like the SL8-6 was used and when completed they do bring big bucks . But some of them are half finished or the first thing they did is get rid of that 10rd.single stack mag well and go to the AR type. HKpro.com is a big forum for HK and they have a lot of articles about that conversion.
Some of those guys have $4,500.00 in those guns or more. I have never seen one for real ,and to each his own ,but for a kit conversion thats to rich for me.
I do know you need to do your homework ,because some guys got some kits requiring grinding and fitting and they screwed it up.