I sent mine to JPgrips on Straight Shooters recommendation. Got it back in a week. $49 includes return shipping. If you have to ship your entire upper like I did then it is another $24.
http://www.jpgrips.com.
I sent him this DPMS Flash Hider ($5.69) and crush washer ($2.19) which he installed for me. He did a really great job.
http://www.midwayusa.com/viewProduct...tnumber=343064
http://www.midwayusa.com/viewProduct...tnumber=333363
Here are the results:
And since this is a S&W forum, here is a pic of "Sweet Lips", my beloved M&P15T: