Search the database for giongo, also known as onomatopoeia or sound effects, and gitaigo, also known as state words or mimesis. You can use the full stop to represent the double consonant. Note that for any words that normally use the adverbial と, such as はっと or ざーと, the と is not present in the dictionary ending, so you should search for these words using はっ and ざー (or, romanised, "ha." and "zaa").