On EFM's website they have a list of dealers and people for service. Perhaps that will get you pointed in the right direction. Hope this helps.
Sadly a lot of EFM dealers have never even seen a coal stoker, and even fewer have ever gotten into a 700. Here is a short list of guys that are knowledgeable about the coal products: efm Dealers/forum members who might have used efm stokers
There are dealers that are happy to supply DF520 parts even if they don't handle them routinely, but it will be a trial and error process to call the ones closest to you and see what they offer.