Probably hard to find a clone of a regional brew. You might just ask to talk to the brewer and see what he based his recipe on. Micro brewers often started as homebrewers and are happy to talk beer.
I’ve even asked for and got free yeast. I just had to plan ahead and bring in a sanitized jar. I got a quart of some very active yeast!
I currently have a cream ale cranking away. That’ll be kegged here in a week or so for a chili cook off. Then an Anchor Steam clone will be ready to keg a couple of weeks after that.
According to Brad Smith, at BeerSmith, a crock was found near Kulmbach Germany dating back to 800 BC with blackened barley bread inside – the standard material used to brew ancient Germanic beer. He says, "The key to making a good Schwarzbier is achieving the appropriate balance between the malt base, specialty grains and hops so that none of these ingredients overpowers the others."
"...The key is achieving the dark color needed without providing too much roasted flavor."
None of the following are attempts to reproduce the wonderful Black Radish, but its a start.
Pitch Black Schwarzbier - All Grain
Pitch Black Schwarzbier - Extract
Schwarzbieresque - Extract
Storm King Schwarzbier - All Grain