Yes, movieposter.com is fine generally. However. I did receive a poster that was in much poorer shape than advertised and they refused to give even a partial refund, so I stopped buying from them. According to Ed Poole of LAMP, moviestore.com is the successor of a National Screen Service branch in Toronto:
There were 4 Canadian NSS branches. They were regular warehousing branches just like most of the other US branches. 3 of the 4 only had small printing capabilities and that was to print snipes, censorship material and press material. In other words, they received their US posters like a regular NSS warehouse and applied the local censorship snipes on them for distribution. That’s why you normally see the US ratings box covered over. Only one branch had full printing capabilities.. the Montreal branch. And that was because they served a very high French public, so they printed the French versions....
The Canadian branches broke from NSS in 1990. Sol [Candel] tried to turn commercial and later made a deal with Moviegoods to liquidate their material. Sol then retired. His younger sister Shelly ran the Toronto NSS branch and has successfully turned her branch into a commercial warehouse. They go under the name movieposter.com....