This is pretty discrete as you will buy it piece by piece, and if you don't buy them all at the same time you won't get them at the same time which there would be no possible way someone would know what you would be making with the pieces. Anyways here is some links to some pieces you would need. The ones I am linking come with two pieces so you would be able to make 2 pipes!
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd2212a#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21ec5#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21eac#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd2203d#ht_577wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21e30#ht_537wt_901
If you would like a colored pipe but aluminum goto this link,
http://www.ebay.com/sch/i.html?_nkw...al+pipe&_osacat=0&_trksid=p3286.c0.m270.l1313
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd2212a#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21ec5#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21eac#ht_517wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd2203d#ht_577wt_901
http://www.ebay.com/itm/TWO-Metal-P...aultDomain_0&hash=item45ffd21e30#ht_537wt_901
If you would like a colored pipe but aluminum goto this link,
http://www.ebay.com/sch/i.html?_nkw...al+pipe&_osacat=0&_trksid=p3286.c0.m270.l1313