Specifically modern items/technology on a medieval setting. I already searched NU so anything here on RRL or an individual site.

If you mean that you are looking for a novel which has business managing in it, then I have something in mind.
Although the MC doesn't really use modern technology, more like slimes, but it has something similar to it.
It's a light read. It can be stupid from time to time, but it's full of crafting and business building and such things. Once you pick up on it, it can quickly turn into an interesting novel. Once again, it's not wholly what you asked for, but I have only this in mind at the moment as I haven't read anything in a long while.

http://www.novelupdates.com/series/the-man-picked-up-by-the-gods/

I don't know if you have read it, but in case you haven't, then you should. You should consider giving it a try. I'm off to write~

yes, i did read it but forgot about it. i will continue this one. thanks! any more suggestions are welcomed :))