You can find some RNAi controls by searching for standard targets.
Looking for positive control RNAi products to validate your experiments? You can find these on BenchSci by targeting your search to standard housekeeping proteins like Cyclophilin B or GAPDH (Glyceraldehyde-3-phosphate dehydrogenase). The product results page should present some suitable control options to peruse.
Controls that are not targeted to a specific gene/protein (e.g. scrambled siRNA) and filtering for RNAi controls exclusively are features that we are still developing, but stay tuned as we continue expanding the platform.