Punch in this item number: 180464135800 (you know where). Now you tell me! Same people I'm getting my Samyang 8mm fisheye from. This could be the most affordable solution out there . . . unless you know better! . . . . . I have no clue about ringflashes BTW, but maybe someone more clued-up can advise.
Otherwise type in: Delta DRF-14 S (or leave out the suffix letter for availability for all makes).
Now if you go to evilBay.fr, the prices are in €, so taking into account exchange rates, you could box clever and get it (or anything else for that matter) for less. Oh, and get 40% insertion fee rebate from TopCashBack if you click via them first and buy. Works for me