https://www.amazon.com/gp/product/B00IHM82XA/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

The 20# round plate on this page (also Yes4All) barely fits in a Rucker V2 pocket, FWIW. Much less convenient than a rectangle with a handle, but it's a single flat chunk of coated metal that you can use for a Challenge (although the snug fit is not conducive to shoving it in like a winner on a time limit).