You'll have to get Age Verified (See this
thread) as per forum rules before we can tell you where to buy the AUG you are looking for. Please check the FAQs section and locate your nearest AV representative. Set up a meeting and provide some ID. Once that's done, you'll have access to Retailers and Classifieds postings that can get you pretty much any gun you want.
As Styrak said, Tokyo Marui or Classic Army AUG A1s would be the best in quality/reliability. If you decide to get the ASG one, expect to have some work done to it (replace/upgrade certain parts) to get comparable performance.