Is that a Seatech fitting? Looks like it could be. I ordered this exact part a couple weeks ago. It's a "stackable elbow" part number 1118-1515. They've been rebranded as AquaLock and the company that makes them is Watts. The black color means they're metric fittings, probably 15 mm. All my local Lowes or Fleet Farm type brick and mortar stores carry only white imperial size fittings and I ended up ordering online from Hamilton Marine. You might have to call around to a plumbing supply store or RV supply. Actually, they might carry it here at the SBO store now that I think of it. If you need it today, you might want to consider a different quick connect brand as long as it's the right size (15mm).