Most all competent builders out there are going to have a similar or longer wait for a build. If you source your own components you can shorten your wait time significantly as most assembly projects are fairly quick from the shops, including GAP. You probably won't find a better example of "spec" than GA Precision though, unless you have a line on an active duty 2112 doing builds on the side.
If you're really impatient, watch the FS forum. I see a GAP 'A5 in there about twice a month. That's how I got my GAP M40A1 and couldn't be happier.