Who doesn't love plague zombies? It baffles my mind that neither GW or FW have made kits for plague zombies. I thought for sure FW would at least make a conversion kit when the 3rd Vraks book was released. Sadly it was not so. The fantasy zombies or terrible and few other companies make decent sci-fi zombies.
Warzone has the undead legionaries which look great but don't really fit in theme wise.
Mantic has a box of 20 plague zombies for $25. I actually bought 2 of these and was not very happy with them to say the least. Don't get me wrong, they are a good buy price wise but the detail was not there and they were just not to my liking.
Puppetswar make the best ones I have found to date but they are not cheap. However, I was forced to buy some as the detail is amazing, quality is great and they fit in very nicely. I bought 15 initially to make sure I liked them and then ordered 15 more. I wish they would sell the arms separate for conversion purposes as they look really good.