There have been several threads over the past couple of years concerning alternative remote controllers for dCS given the price of the dedicated one.:
I would suggest that Logitech Harmony is your best bet if you just want volume control. “Bartok” will not appear as a product in the Logitech list of programs but just select another dCS product. The volume codes are, I believe, identical for all dCS DACs .
Please note, however, that Logitech have announced the discontinuance of Harmony during the past month. Therefore you will need to act swiftly to find offers of exisiting stock. Logitech have promised future support however.
Another alternative is to copy the codes from an existing dCS remote to a learning remote ( e.g. Apple). You obviously need access to a dCS remote to do this and i would suggest assistance from your dealer if you do not have a contact with one.