Been experimenting with cheap curved-end straps for my Sinn U1 following the unsuccessful purchase of a used Sinn silicone band that proved significantly shorter than claimed by the seller...
The one below appears to be based on Omega Seamaster dimensions
judging by the pictures on Ebay, and proved quite impossible to fit to the Sinn until I attacked the plastic reinforcing piece at the head-end with a Dremel reamer! The final result being a decent fit that I'm really rather pleased with.
Quality is easily on par with Barton's 2-tone straps, so for £14.95 I'm rather satisfied: