there are lots and lots of Web Stores that sell clock kits. The problem is tracking the prices they charge, and the quality you get.
But some places to start you looking:
Klockit:
http://www.klockit.com/default.aspx
Steebar:
http://www.steebar.com/
Woodcrafters:
http://www.woodcraft.com/
Wildwood designs:
http://www.wildwooddesigns.com/
Some like Bear Woods Supply:
http://www.bearwood.com/
(note: be sure you get the correct web page, US, or Canada/International for the prices in USD, or CDN.)
BTW: on the left hand side of this forum site, there is a section call Scroll Saw Community. Look under that section for the link called Other Great sites. Work you way thru to the retail on line shops, many of them also carry clock kits.
Other members of this forum will chime in with their recommendations.
Be aware, there have been reports this holiday season of slow response time from both Steebar, and Wildwood design. I have never heard of a complaint against Klockit that wasn't resolved quickly. Klockit is very slightly more expensive. Also sometimes a better product.
Phil