Congratulation on that steal.
In this day and age, almost ANY N-frame in good operating and cosmetic condition is worth $700+
But getting a rare piece like that one at that price is almost criminal. Product code 101024 almost always sells for double that or more on the auction sights these days
A correct checkered rear sight is going to be almost impossible to find for a -1. Only a small amount of -1s and tiny number of -2s had checkered rear sights. If I had to guess, I would say the total production of both engineering revisions of the checkered 627 was under 500 pieces. The remaining ~4800 top strap checkered 627s took the same rear sight as the carbon steel Model 27s so those are abundant by comparison.
Your best bet is to just get an uncheckered rear sight for a drilled and tapped N-frame and keep looking for a checkered one.
Or what would be so very much faster is to take the uncheckerd rear sight to a gunsmith and have it checkered and re-blued