Try horizoneslchina.com. They have very helpful English speaking staff. They are upfront with the details of your contract. They also take into consideration where and at what school level you want to teach. I did not end up taking a job with one of their schools, but they shopped me around and arranged several interviews between myself and some schools. The fact that they actually arranged some interviews and did not just give me an offer during my first contact showed something of their seriousness.
If that does not work, you can try teachinjiangsu which you can find here on the forum. I ended up signing with one of their schools. They offer a standard contract at government schools and everything they promised has materialized. The only drawback is that they are limited to placing teachers in Jiangsu.
I hope this helps. Juan.