You won't need a new ECU.
If you search this forum by typing this command in your browser (include all the words between the quote marks, but not the quote marks themselves)
"site:
http://forums.sv650.org lost ignition key"
You'll see many people that have had the same problem and the suggestions. I looked briefly and some say a locksmith will be able to cut a new key for you (if they have the lock). It doesn't appear that Suzuki cross reference the lock number to the VIN.
There are a few used lock sets on ebay which might be cheaper than a locksmith and I also saw this which looked interesting:
https://www.ebay.co.uk/itm/Ignition-...kAAOSwO-pcVIsg