There are TFTP servers, as Johathan suggests, that are capable of handling large IOS image files. Two that I have used with success are 3Cdaemon and TFTPd32.
However as the image file size increases I believe that there is a real case to be made for using FTP for the transfer rather than TFTP. For one thing there is no size restriction when using FTP to transfer image files. And the transfer with FTP is much more efficient than the transfer with TFTP. Using FTP your transfer will be much more quick than when using TFTP, and as the file size increases the performance difference gets more obvious. So in your case FTP would be a good option to consider.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...