A couple things to consider-
*You stated you have searched and cannot find that model or another brand with the same/similar floorplan. So if this is something that has to happen now, it may boil down to settling on that price or another model.
*A brand new hard sided camper at 10K isn't easy to find. I have seen units at RV shows listed at $9999 and they were usually bare bones entry models.
I'm not saying to buy or not to buy, I'm not you. You have to decide if all the bean counting and pounding the pavement will pay off, or if when all is said and done, the camper on their lot is worth it.
If you decide you have to have that one, I'd probably get my financing lined up, go back in a week with a check for 12K and explain, this is what I have to spend. Either they will sell me a unit at that price or someone else will. Just depends on who wants the check bad enough.