I've done a search of Ebay bargains for The River King DVDs. These are the best deals I've seen, if you'd rather not pay full price via conventional services.
There's an auction currently standing at US$2.55- it's had 2 bids already (the seller has no history)
This one is a 'buy it now'- for US$6.10 with free shipping (only in US)
From Ebay stores (safer in terms of buying), there's one for US$12.99 plus shipping, and one for US$13.04 plus shipping.