Those clamp on ones John suggests would work but to my sensibilities they just look way too ugly for words.
When you consider how many frames were made in the past and are still made now with expand in place "brazeons" drilling for two small rivets is not a big deal. Bedding them with a glue such as CA or epoxy isn't a bad idea either but too many things can happen over time for me to trust a glue only situation unless the brackets have wings that wrap around to increase the surface area of the bond and make the stops look like old tyme lugs. Add to that the requirement to sand or otherwise remove the paint in the joint area and it just seems like more work than drilling for rivets. But for just bedding the stops so they can't wiggle around just scuffing the paint right under that area by masking off the surrounding area will form enough of a bond for just bedding things down. If you sand the spot through to the metal then that's a bonus.
Chombi, in this case there's no requirement to ease the corners. Stress risers come from cracks in the metal. A raised burr from drilling a hole just does not qualify as a point that will stress into a crack.