Like you, I am unaware of any SAP-specific security credentials, either from SAP or from third-party organizations. Thus, your best bet is to pursue a good, general, well-recognized security certification like the CISSP. I don't think you'll need to switch your area of focus from SAP to something else to get certified, and wouldn't recommend such a change unless you have other compelling reasons to make one. If you're making a good living doing SAP stuff, a CISSP will provide more objective "proof" of your general security skills, and you can keep doing SAP stuff (hopefully for even more money, to justify the time and effort involved in getting the CISSP under your belt).
If you do have further questions, however, feel free to ask away. Thanks for writing.
This was first published in May 2003