Daschunds
The DBAX-34 and FDAX-34 are Atomic Zombie part numbers. But are not longer produced by Atomic Zombie due to cost to build and ship by AZ. There is nothing like them on the market presently.
Nanango gave you an Amazon link for Freewheel adatper to mount a freewheel to an Axle.
What you can to is DYI using Shaft collars for the DBAX-34 and piece of metal cut in a disc. Alternatively you can use large Flat washers welded to the Shaft collars.
For the FDAX-34 you can buy the Freewheel adapter and weld a large metal disc or flat washer to it and drill hole for the Disk brake.