I'm assuming you're talking USA and the limited edition. If so Amazon is currently the cheapest I believe.
If you mean the Japanese Collectors Edition your best bet would be something like Play-Asia.
It looks like this one: https://www.amazon.com/Your-Name-Limited-Blu-ray-Combo/dp/B074QVZD11 From what I've seen on unboxings, the cover has a really nice prismatic shimmer. Also comes with a 60 page art book, and a 2 CD soundtrack.
Amazon actually had it up as a lightning deal on Tuesday for $47.99. I think only 40% of their sale copies were claimed though, so hopefully it gets another big discount soon. (Mine is arriving today. Hurray!)
I didn't know they had a steelbook for this. I have this version.
It's not really something "unique", but the Limited Edition Blu Ray Box for Your Name is absolutely amazing. Might be a good buy
Currently back ordered on our site, you can grab it here though: https://www.amazon.com/Your-Name-Limited-Blu-ray-Combo/dp/B074QVZD11/ref=sr_1_1_twi_blu_1?ie=UTF8&qid=1510165200&sr=8-1&keywords=your+name+limited+edition
AFAIK, american “limited edition” is not 4k. (Your Name Limited Edition [BR + DVD] [Blu-ray] https://www.amazon.ca/dp/B074QVZD11/ref=cm_sw_r_cp_api_n1IYzbPBK8PFB)
You can pre-order it with the book in english now, but will have to wait till Nov 7.
I had trouble finding it too. Here is the link for the Amazon US listing: https://www.amazon.com/Your-Name-Limited-Blu-ray-Combo/dp/B074QVZD11/ref=pd_lpo_sbs_74_t_2?_encoding=UTF8&psc=1&refRID=BCN1ZNG4FC3H4D0S03RR