https://www.rocketryforum.com/threads/kteshs-openrocket-files.123564/page-6#post-1582471
I usually have good luck finding them via google search. Just search "mega mosquito open rocket file". The link above came from the first result, which was to the RocketReviews website, which is a good source. Funny enough, RocketReviews just linked back to K'tesh's OpenRocket files thread.