I have found these open-end straps to be comfortable and a great solution for watches with fixed lugs. They come in 5 sizes (12-14-16-18-20mm), several colours and have colour-matching stitching.
They come in smooth calf leather, buffalo grain calf leather and croc grain calf leather. Their length is approximately 85mm on the buckle end (including the buckle) and 115mm on the tail end (75/110mm for the 12 & 14mm); so not short but not too long either. Tapering is 2mm. They are supplied with a steel buckle. If a gold-plated buckle is preferred, make a note in your payment and I will replace it for you if I have it in stock. They have two keepers, one of them is fixed and the other one is floating, for a better fit and comfort. Feel free to contact me for whatever questions you might have.
P.S. For a permanent fitting, they should be fixed using super glue. For better results, we offer a set of clamps that is to be used for this exact reason. You can see them in the last photo here and purchase them separately, as they are listed elsewhere in our store, under Accessories & Straps.