My experience with Keenovo is very positive. Simply state what you need, mention the voltages and the dimensions of the pad and the shape, and they simply make it the way you asked for. For the 20 to 30 euro extra I'm not going to make my own digital thermostat, others do this cheaper, they are produced in great numbers. The same is true for the 12V power supply coming from the yellow and black of an ATX power supply. And yes, near all warping and smudging of PLA has disappeared, you may want to start with a bed at 80C for the first few layers and then turn the thermostat back to 65C.
https://plus.google.com/105007223477973316510/posts/291Uf3d48fn
https://plus.google.com/105007223477973316510/posts/YkW3SkHazfr
Blog post that summarizes the modification and the results:
https://ejo60.wordpress.com/2015/05/09/add-a-heated-bed-to-your-3d-printer/