Hi,
Chinese smartphones are those that are including these features in their latest models, if you don't want to buy a generic device (aka: clone) it would be advisable to look at some Chinese manufacturer that already have some track in the market like: Huawei, Lenovo, ZTE.
The latest models that seems to fulfill the requirements that you mention is the Huawei Honor 3C 4G (LTE), but there are some dual sim phones that handle 4G (HSDPA+), so maybe you have to decide which type of 4G connection you require LTE or HSDPA+ and from there the options to buy will increase.
By the way, don't forget that you will always get access to 3G as long as all the latest dual SIM android devices allow this type of connection.
Regards