I would suggest taking a look at War of the Burning Sky (<a href="https://marketplace.roll20.net/browse/publisher/230/ancris-it" rel="nofollow">https://marketplace.roll20.net/browse/publisher/230/ancris-it</a>). It is an AP that normally runs levels 3-20, but it has an options for various abridged campaigns using subsets of the adventures, and the adventures have means of adjusting the encounters for parties a level above or below the intended starting level or larger or smaller than 4 PCs. You could jump in at The Mad King's Banquet (<a href="https://marketplace.roll20.net/browse/bundle/3843/wotbs-the-mad-kings-banquet" rel="nofollow">https://marketplace.roll20.net/browse/bundle/3843/wotbs-the-mad-kings-banquet</a>) at level 8 and just not level them up until the end of the adventure. I'll PM you links to the player's and campaign guides so you can decide if it makes for a good fit for your existing campaign (of course, you and your player's might want to start at the beginning!).