Here it the Unistrut website. There is about any piece and part you could want. http://www.unistrut.us/index.php The common angles and straights are pretty readily available from your local Big Box store or local construction supply store. The oddball stuff you will probably have to find on-line. Most places will only sell the oddballs in bulk. So someone will buy what they need in bulk, use the 2 pieces they need, then sell the rest.
I used the P1000 1-5/8" x 1-5/8"
and the P3300 1-5/8" x 7/8"
I used the P1000 1-5/8" x 1-5/8"
and the P3300 1-5/8" x 7/8"