Hi! Sony produces repair parts for this camera and they are purchasable by an end user. Sony and Panasonic use "encompass parts" as their sole supplier for repair parts. The repair parts are sometimes not that affordable, but they are genuine parts, not knockoffs. In this case, the Sony A7RII is actually called ILCE7RM2/B internally by sony. So to find parts for your camera, go to www.encompass.com/ and search for your model. In this case, ignore the "/B" as nothing comes up and it probably stands for the black color.
When searching for ILCE7RM2, a list of parts come up. In this case, here is your viewfinder assembly:
encompass parts phone # (800) 432-8542
If I were you, I would verify with encompass parts that this is truly the correct part. I have called them and they will check this for you. If you ask them for a parts diagram they will usually provide that for you too, so you can get a better idea of what part you need. I've tried asking / buying a service manual for Panasonic cameras and they wouldn't sell me one. They claim that you have to be a Panasonic repair technician to get access to the manuals. I don't exactly buy this explanation, but I figure I would mention if anyways.
It has been common to bash canon lately for under-performing cameras and ones that are missing features, but they are indeed the easiest to get parts for. Canon is one of the few camera companies that has a dedicated repair parts hotline. You could literally call them, ask for a part and they'll let you buy it in the same phone call. You don't have to be a a certified retailer or supplier or technician. You don't have to go through a 3rd party. They really should get more credit for this.
I have personally called them for a 5D mark II viewfinder optical component because I foolishly used alcohol to clean the back of the viewfinder. The alcohol turned the plastic viewfinder lens opaque and rendered it useless. The genuine canon part was ~$32 after shipping. It came to my door within 5 days and I spent less than 5min on the phone ordering it.