Apologies for this delayed response; we're still awaiting word back from our Devs as to whether that beta feature has been removed permanently due to low interest/usage, or just temporarily pending a revision.
Meanwhile, we can recommend a different approach to accomplish much the same thing:
Simply add the buyer's items to a cart -- you can do this with Add to Cart buttons from your site or E-junkie Shop, or directly from your E-junkie Dashboard under Manage Products > Get Purchase Buttons/Links -- then click the Share icon in the cart (sideways-V icon next to the cart icon at the upper-right corner).
This will copy a link you can paste into an email (or other message) to the buyer. When they click that link, it will bring up a shopping cart pre-populated with all the same items you'd added to cart before clicking the Share icon. From there, they can then proceed to checkout using any payment method you accept.
