If you're wanting to make some different Turkish foods, I'd hazard a guess you enjoy cooking, so why not make your own? I found a recipe classed as 'Easy', taking 1 hour to prepare and 50 minutes to cook. I read it has the consistency of tomato paste (contains no tomatoes) and looks to be from the photo.
Among the list of ingredients is bullhorn peppers. Perhaps a local name but when I looked up what they were, they looked exactly like Hungarian sweet peppers. The name 'bullhorn' comes from their shape as they curve and taper to a point like horns. Here's a photo:
Give it a try! If you really enjoy the Turkish recipes you make, you'll likely want to make them again so having some biber salçası around will come in handy.