This certainly is a problem. A bunch of us developers in the community have been trying to find a USB GPS solution for WinRT, but as is the case here, there are no drivers available that we can find for *ANY* USB GPS product. None, zero, zip.
The problem appears to be that Microsoft may be unintentionally impeding the process since the manufacturers of these devices have not been able to acquire the requisite sdks or signing permission (for the device app since they have to be signed to run)
to do so. Another problem is that Windows Store Apps don't have the necessary access to the USB device even if the driver existed. So it's a big problem. We've posted on forums and tried contacting Microsoft directly, but so far nothing.