If a single matching dropout cannot be found you will need a matching pair and there is nothing half assed about repairing a dropout if the work is done well.

The decision to do this would have to be based on the frame being worked on... if it was rare bike would want the correct dropouts to be used but if the frame was to be used as a daily driver a well repaired dropout would work fine.

Those Suntour dropouts do seem prone to failure as I have seen more than my fair share of them with cracks at the same location... they are rather fine and seem to suffer most when they are used on bikes that see harder use like mtb's and touring bikes.

That Miyata dropout (a Suntour) had a small filler piece added to strengthen the cracked area and it's owner is a six foot five guy who curbs out at 240 pounds and lays down a lot of power... this was information that my frame builder had before he did the repair and his suggestion was to repair it and increase the strength in this area rather than replace it with a matching dropout.

He's been doing this for 30 years... I trust his advice on such things and his pre-frame building experience was as an engineer, machinist, and welder.

He does have a "pretty is as pretty does" attitude towards building frames and parts and I have known people who have ridden his frames and hubs around the planet and never had a moment's worry about them failing.