I prefer the factory grips, the Hogues are a little to big for me. I don't know of any others that are available for the 6906. The 6900/Shorty-forty/4000TSW compacts all use the same grips, they run about $20 from S&W or Brownells.
I find the wrap around grips to be too bulky on this type pistol. I stippled the factory grips as did many others on this forum. I prefer this setup for a carry pistol.