Transgender breast implant revision. Do 1000cc silicone gel implants exist? (Photo)

Hi in the US the largest off the shelf available FDA approved silicone implants are 800cc.  Larger silicone implants can sometimes be custom made as well. Though keep in mind, extremely large implants greater than you body's breast footprint can lead to issues down the road with skin stretch, drooping and synmastia which can be very difficult to treat.
When you overfill saline significantly it will often feel firmer because it is on stretch and unable to easily compress.  If from the time of surgery these firm feeling has been there then it likely is due to the large overfill.  However if this is a change or causing increasing discomfort it could be due to capsular contracture.  I would recommend returning to your plastic surgeon or seeking out a board certified plastic surgeon for an in person exam to help determine the cause of your issue and see what solution may be possible.
Best of Luck!

Thank you for your question.  Based on your history it appears that the firmness may be because of capsule formation. 1000 cc silicone gel implants can be customized.  Some autologous fat can also be injected for a smoother result. Please find an experienced Board Certified Plastic surgeon who can examine you and help you with all your concerns. All the best!

Thank you for the excellent questions and photos. Personally, I feel that a larger sized implant will have bad longterm consequences for your breast shape and skin laxity. Over time, you will likely experience too much stretch on the skin and this will result in a ptotic or drooping shape. It appears that you already have implants which are quite large for your chest wall dimensions. Larger implants will also put you at risk of developing symmastia where you lose the separation between the breasts (uni-boob). This can be difficult to correct surgically. 

Thanks for including your photos. The saline implants are always going to be more firm, especially if they are overfilled, but if you notice one side is a lot firmer than the other, you may be developing capsular contracture. Silicone implants current are made up to 800 cc, however they do come in custom sizes - you should ask your plastic surgeon to talk to the implant rep about these if you are thinking of pursuing that route. Capsular contracture can still happen around silicone implants, and if there is a high degree of contracture around the current implant, you may also want to consider partial or complete removal of the capsule at the same time you have your implants exchanged.