Oddmott.
Try Trulock Chokes. They carry them in just about every thread, and maker out there. I have a Mossberg SA-20, basically the same Turkish Manufacturer as the SA-08. They have them for both.
http://www.trulockchokes.com/get-cho...kes=See+Chokes
Service was great. Don't order online though, call them, Their customer service dept will make sure you get exactly what you want, and will ship USPS rather than courier to save on shipping costs.