I'm pretty sure there are no silver slides out there for the P99. So what you could do is, paint the slide silver. Or, get a zeke slide and remove the black paint, and you'll be left with a nice silver underneath. This may be tricky though, I've never tried it myself so this is just speculation. As for the LAM, this is the closest I could find. Unfortunately they dont seem to be selling it seperately.
http://www.dentrinityshop.com/pr_details.jsp?pid=2813
Or, you could get the real steel LAM for the small fee of $375 US.
Link here:
http://www.carlwalther.com/p99acc.htm (3rd one down)
Pic here:
http://www.carlwalther.com/images/p99_laser_ba6_a.jpg