I'd also suggest using the existing rear hub & 6sp freewheel. Build a wheel around it using new spokes and a new or good used rim (if used, inspect it closely). You should be able to find a rim that is similar to the front wheel. If you don't want to try building the wheel yourself, perhaps there is a fellow bike rider that may want to do it in exchange for Guiness or something. Building wheels is not that difficult, but definatley time consuming. Make sure to get a good instruction book if you plan to try it yourself. A rear wheel is trickier than a front because of the "dishing" required to offset the freewheel.

Another thought, depending on how bad the current wheel is damaged (I haven't seen your pics)...
Can you do a rim swap and use the current spokes? That is pretty easy if you can tape the new rim beside the bent one, swap the spokes over and then true it.

Best wishes!