I've been looking around the net and found the parts on different sites. After finding the gas piston conversion, I added it to my parts list. Here are the costs I have figured as it stands.
$787.28 AR-15 (w/o gas piston conversion)
$1,116.50 AR-15 (w/ gas piston conversion)
These costs include the shipping from the sites where I found the parts. I may stay with Direct Impingement until I can build enough funding to get the conversion and install it on my AR. If desired I can post all the information that I have in my spreadsheet for all the parts and where I found them.