I recommend the Borderline Personality Inventory developed by Leichsenring (1999). I use the Polish adaptation of it and it works really well. Maybe you should contact with the author?
Leichsenring, F. (1999). Development and first results of the Borderline Personality Inventory: a self – report instrument for assessing Borderline Personality Organization. Journal of Personality Assessment, 73, 1, 45-63.
IPDE (International personality disorder examination) - training run by the Institute of psychiatry. Excellent tool, but takes a while to do. The IPDE was developed within the Joint Program for the Diagnosis and Classification of Mental Disorders of the World Health Organization (WHO) and U.S. National Institutes of Health (NIH) and provides a uniform approach for assessing personality disorders for both the DSM-IV™ and the ICD-10 classification systems. The interview is the most widely used of its kind and is the only personality disorder interview based on worldwide field trials. The IPDE Manual contains the interview questions to assess either the 11 DSM-IV™ or the 10 ICD-10 personality disorders. The two IPDE modules (DSM-IV™ and ICD-10) contain both a self-administered screening questionnaire and a semi-structured interview booklet with scoring materials.
I'm confident with psychodynamic framework only. In my opinion, the DIB-R is the best for Borderline Personality Disorder, according to Gunderson/DSM. On the other hand, the Structured Interview of Personality Organization (STIPO) is a well-supported tool to assess personality structure/dimensions according to Kernberg/PDM.
It depends whether you would like to use a self-report or (semi)structured interview... If you are looking for an interview, the IPDE or the Borderline Personality Disorder Severity Index (BPDSI, http://www.ncbi.nlm.nih.gov/pubmed/12659546) are usefull. The Schedule for Nonadaptive or Adaptive Personality (SNAP; Clark, 1993) is a self-report with good psychometric properties.
If you're happy to use self report to measure borderline traits rather than a clinical disorder you could try the personality diagnostic questionnaire four by Hyler. It costs but is relatively inexpensive.
A good and short (self-report) measure for cognitive characteristics of patients with BPD is the Questionnaire of thoughts and Ffeelings (QTF) by Renneberg et al. (2005). It also discriminates very well between patients with BPD and other clinical groups.
Try with STIPO by Clarkin, based on psychodynamic conceptualization of Kernberg. (http://www.personalitystudiesinstitute.com/pdf/Structured-Interview-of-Personality-Organization.pdf)