Hey, I’d like to preface by saying that I’m no audio engineer so to judge whether this plugin is “good” or not is slightly beyond me, but I did find a potential solution for you, sounded alright to me.
So one free option that could do the job is Graillon.
Use the installation .exe and for Vegas Pro 17 you’ll need the VST2.4 version. I believe starting with Vegas Pro 20 you can use VST3 version. Install, restart Vegas Pro and it should be added automatically.
Then you need to add this effect to the whole track, not the audio clip. After that I’ve attached screenshots of where to find the fx automation button and then look for pitch shift. Tick that, click OK and you should get an envelope for pitch shift on your track. Then add your points and you’ll get a gradual pitch shift.
My screenshots are from VP20, but functionally the process is the same for VP17 – tested, worked.
The free version does still offer some customization, you can tweak some settings, but some panels are locked.