Several years ago while on a back country hunt I slipped & fell on a frost covered Aspen log. The rear of the scope hit the log & bent the eye piece. My open sights saved my hunt & allowed me to take game & have a successful hunt. My advice , if you still can, replace the sights. They work when a scope fails.
With my luck, a fall like that would cause me to lose my glasses, so irons wouldn't help! And irons can be pretty fragile themselves, especially the front if there's no hood.
Another option for backup, if you use Weaver bases or a rail is to carry a small red dot like a Fastfire. Pop off the scope, pop on the red dot, and off you go. I hunt close to home and not much more than a mile from my car, so I can do without backup.
For certain, if you want irons, better buy a rifle that has them already. I was looking at the price líst for smithing services the other day, and holes were $65 each.