ABS Enclosure Design question

Hi,

We have an existing product that we would like to modify. The current enclosure is a simple black ABS rectangular ( 4x6x2 ) off the shelf enclosure, with cutouts on the side for connectors.

Now we would like to add a COG LCD on the top cover, but we have no idea how to attach it to the enclosure. Therefore we are thinking about a custom ABS injection moulded enclosure.

Do you guys know of a company we can use to help us design the enclosure ? We would like to manufacture it as cheaply as possible so we are thinking that a chinese manufacturer would be a lot cheaper than a US based one. Either way we don't know where to start looking.

Thanks