Hidalisa in POP do have some nice stuff, if a little pricey but reasonable quality. Distribudora Gonzales too. They've already been mentioned, but just to back it up.
If you're after rattan I can highly recommend Yvonne & Otto who run a mimbre & rattan furniture factory in Sosua on the main Cabarete - Sosua road opposite(ish) El Choco. It has a large rattan chair up on a pole at the entrance.
They can make anything you want. They have a very nice showroom or you can thumb through their various catalogues and choose something and personalise as you want. Or you can even go in with a magazine cutting or something you have printed off the internet and they will copy it perfectly. Their turnround is very quick, prices very reasonable and very pleasant to deal with. They are a German couple but speak perfect English.
For cheaper Dominican style furniture I can recommend a store in Gasper Hernandez. I don't recall the name, but it is probably the only three storey store in GH. Prices are more on par with Santiago, which is less than most of North Coast.