Most of the show leads we use are ordered from Leading It. They make wonderful custom leads and often have a great selection of pre-made leads available.
We use different leads for different dogs. I prefer the kanagaroo, goat, or deerskin for the smaller show dogs. We have found the thicker braided paracord leads are great for our bigger dogs. We generally order our leads in 40" length with three sets of beads which makes it easy to hold the lead at different points as needed during a show. Leading It has reasonable prices and can make anything you need.
We have found Petedge is the most reasonable place to order this brand of show collars. If only needing a couple, they can also be ordered from Leading It. Petedge offers a wide variety of pet and show animal products with free shipping on all orders over $150 as a promotion they run often.
These are a great lead for someone starting out showing, or to keep as a backup. They can be purchase for about $10 on Amazon. They are great quality, but inexpensive.