I checked amazon for the hilleberg allak and it costs 140k yen, and says it usually ships within 1 to 3 weeks. On Amazon US the same tent is about 30k yen cheaper.

One suggestion is if money isn't a big problem you could just get it the hilleberg tent off amazon, or you could get a tent from Amazon that is around the 30k price range and get the hilleberg once you're back at a lower price.

I don't have experience with mont bell tents, but I have a friend who uses one and he says it works great. I own a few of their products and they are all good quality. Although a quick glance through their tent lineup, they don't seem to have two entrance, but some do have a porch.

Just as an example, this tent is in stock and costs 22k yen, and from my experience with Amazon Japan it should be in your hands within the week, given the seller processes the order in a day or two.