Yes, we have one, but it's too difficult to keep up to date, and is not an exact replica ... so it wouldn't solve your problem since you need to test before you ship.
Our preferred approach is to extend the range of linux systems you can use for WT Sparks development. If you don't adhere to the strict one-size-fits-all sparks configuration recipe we provide, you can actually get an inexpensive system for WT development.
In fact, just about any 64 bit capable system will do. Other Sparks developers already take advantage of this.
Dan