Start with asking BMW Taiwan.
If BMW Taiwan have no maps, then ask other car makers that use VDO Dayton maps:

VW
Porsche
Opel

If none of those have any maps for Taiwan, then you need to find a very clever software programmer to make you a map. These people are few and far between. I know one in Russia.

Unfortunately, map file formats are proprietary and there are no tools to convert maps from one format to another.