you will find no rear sight replacement for the 717-747, you might think the metal sight for a 777 would fit but it will not and there are 2 reasons there are no sight and the clam shell are different 

you can find 777 grip from time to time or you can have Vernon Austin make you some and he is on Ebay also 

https://www.ebay.com/sch/mystryman_1/m.html?item=132366956852&rt=nc&_trksid=p2047675.l2562

you could scope the pistol using a IZH 46m mount 
 
there is one other thing when people thought of using the 777 rear sight on the 717-747 pistols it would not have worked any way the front sight om the 777 is taller besides the clam shells 

Bio is right on the rear sight, it is fine 

i have 717 hybrid, with 747 trigger group and barrel and 777 grips 

the trigger group can be improved but you have to y=understand how the trigger works and that work can be done out of the pistol, you can add a piece of, i used stiff foam on top of the trigger assembly to take up the trigger travel, it just push the trigger down to take up the travel 

not a perfect fix but a proof of concept
 
I have several 747s and a couple 777s and prefer the 747. I don't find the sights on the 777 that much better. I would suggest getting extra sights, valves, and seals from Daisy while you can. They are way cheaper from the factory than on line. Also I have several grips from Vern including Birdseye Maple and they are excellent. He also makes them in right, left and ambi handed. He can make them in different sizes. I'm a lefty with smaller hands and he made me some smaller ambi ones.