Any over-the-counter help for someone with syncope?

No. There are too many possibilities. Syncope (loss of consciousness) may be due to a simple faint (vasodepressor reaction) or be due to serious, even life threatening conditions such as certain disorders of cardiac rhythm or valve disorders. Before any treatment is considered, evaluation and diagnosis are required to rule out the dangerous causes.
Depends . Depends in the cause, but if vasovagal, then otc salt pills can help; however, check with your doctor to ensure they won't interfere with any of your other medical conditions.