These Bicycle Rider Back decks aren't new, as far as I know. Your Walmart may have simply received some old stock lying in the back of the warehouse. They aren't custom - they were produced by USPC, not a third party.
Conjuring Arts Research Center (conjuringarts.org) used to have the silver Rider Back deck in stock; sold them out a while ago, aren't expecting more. They were manufactured by USPC in 2009. I think the pink ones are at least as old, maybe even a little older - I've seen playing card retailers selling them for years. One retailer even added an "It's a Girl!" sticker to it, as well as an "It's a Boy!" sticker to a matching baby blue deck of the same design.
There's been a couple of different versions of a purple Rider Back deck, including one from Magic Makers that included gaff cards for magic use instead of ad cards. They aren't hard to find if you check with magic shops that sell cards or card specialty retailers online. Amazon.com has them as well. They aren't terribly expensive as collectible decks go because demand isn't very high.
If you like color variations of the Rider Back design, Vincenzo DiFatta produced a boxed set sold in some magic shops - nine different colors of Rider Backs plus two inexpensive close-up mats (one red, one black). The deck colors are red, blue, black, gold, silver, orange, green, fuchsia and turquoise.
This company's offering it through Amazon at a decent price, considering it's a collectible item these days:
https://www.amazon.com/Bicycle-Color-Collection-Decks-Tricks/dp/B00NI5C0M0Simply put, of all the Bicycle designs over the years, there are more variations (color and colorway) of the Bicycle Rider Back than any other card back design, and perhaps more than all the others combined. These days, most people who aren't card collectors know the design simply as the "Bicycle design" because when the company moved to Erlanger, Kentucky in 2009, they removed the design name from the box as part of a tuck box redesign with a slightly more modern look, simply calling them "Standard" - which refers to the size and index type rather than the back design.