The wxWidgets packages are in the OSS repository. This repository is at this URI: http://download.opensuse.org/distribution/12.1/repo/oss/
and should be part of your 12.1 installation unless you have removed it.
Packages are installed using:
YaST >> Software >> Software Manager.
If the OSS repository has been removed, it can be added using
YaST >> Software >> Software Repositories.
As with the OSS repository, it would have been added as part of a standard installation. To use it just select On-Line Update in YaST2, or use
YaST >> Software >> Online Update Configuration
to enable automatic security and recommended updates.