Try your local TH authorized dealer (AD). I was able to get new links for two different Link watches a couple of months ago from my AD, and the prices seemed very reasonable -- the steel links were $10 each, plus shipping.
The prices on ebay for genuine TH links are ridiculous, and I wouldn't buy from there unless they weren't available anywhere else. I have also seen listings for aftermarket/clone links on ebay, and even those are more expensive than my local AD.