Depending on the style and quality you need, and whether you need pictures of very specific items or just want "a sword", it's not too hard to render them, maybe toss the result through an artistic filter. In that case you just need to find/buy 3D models (with free ones you also have to check if they are free for commercial use).
E.g. rendered using Reality for Poser, run through PostworkShop and layered over the originals, posted at reduced resolution. This is probably an unnecessarily convoluted workflow though.
Aside from that, I would suggest wandering through DeviantArt and look for someone with a suitable style that looks like they are not a highly-paid professional, then message them and ask. There are a lot of people who will do commissions, but it's not always cheap.