I called Anderson Pots/Anderson Die, and they informed me that they are strictly wholesale only. I did check several of the distributors listed on their website, and found only two that allow you to order online.
Grower's Nursery Supply is located in Salem, OR and has a
20-pack of the 2405B for $60. Shipping to my door in southern Utah would be $62.
OBC Northwest is in Canby, OR (Why are they all in Oregon?) and has a
25-pack of the 2405B for $107 plus S&H. It tells me to call for a shipping quote, so I am not sure that this qualifies as "order online." Regardless, I imagine the per-piece price including shipping is probably close to or slightly more than Grower's Nursery Supply.