Not to my knowledge. SideArmor was reportedly working on a rail adapter but has never announced anything. Now that the P99 frame is changing to conform with the SW99 and S&W Tactical pistols, they may no longer be motivated.
I believe that GG&G is working on a rail adapter as well (http://www.gggaz.com/). At least I hope they are working on the adapater, they have had my pistol for measurements and mock up work for the last month. I will post more when I get the pistol back. It is supposed to be very similar to the HK adpater they have as the rails are similar. The adpater will mount M3, and M6 lights. I'll keep you posted.