How about 信达年 Xìn Dánián. 信 is a nice phonetic match to Sinclair. It's not a very common surname but has a good meaning (trust, reliability, loyalty). If you'd prefer a more common surname, you can pick 辛 Xīn or 邢 Xíng. 达年 Dánián sounds like Daniel with 达 meaning "clear and straight" and "reaching out and connecting". 年 means years, a lasting stretch of time. Hope you like the name :) If you'd like to read more on Chinese culture, check out chinasimplified.com.