Digikey has over 100,000 Atmega2560 chips available, that can make a ton of boards.
https://www.digikey.com/products/en/integrated-circuits-ics/embedded-microcontrollers/685?k=atmega2560&k=&pkeyword=atmega2560&sv=0&pv1291=2491&sf=0&FV=ffe002ad&quantity=&ColumnSort=0&page=1&stock=1&pageSize=25
I even offer boards in a smaller form factor, no 5V regulator or USB interface on board for flexibility.
