Just about any competent roofer can correct this. I would suggest finding a vent that you like yourself and providing that hardware. I say that because most roofers are going to be at the mercy of whatever the supplier has in stock. They might shop Home Depot, but again, whatever the store on University has is what they'll get. That is not always the best and likely why you have an airhawk on it now. You may also want to do a little legwork and research and see if you can see the pipe in the attic. I can't tell you how many roofs I have done where a pipe comes up short, or it's the wrong kind, or it's this or that, and when the roof is torn off, I am extremely limited in how I can deal with that. So, take a peek, or make sure your roofer can see if first so they can be totally prepared. It will save you some hassle and lead to a better, one-trip fix.
I like the more expensive ones, but the 6" gooseneck they have locally will suffice.