Sissiors are an important item in the sewing kit. I use both original and modern, originals for the demo stuff, the $10-15 Fiskars for home use. These Fiskars are their bottom line type, but I get several years out of them, depending on how bad I abuse them. I keep the edge for a long time with a kitchen steel and throw the away and buy a new pair when needed. This is cheaper that having good ones sharpened. (In reality I convert them to fine paring knifes but thats belongs somewhere in another thread)
I have several pair that are maybe 75-100 years old, the bad thing is, most need sharpened, and the bolts in the hinges get worn and they have often been abused. I have a pair I hand sharpened and replaced the hinge bolts in that are my large 1 gallon can sewing kit. this pair also had the point in one side broke and has the ends ground round, often seen on old sissiors.
For smaller kits the buckskinner suppliers offer a small sissiors that look very period and are made in China, cost around $5-7 dollars. The ones I've seen are very good steel, rumored to be made out of the springs of the 2 1/2 ton trucks and jeeps we left behind in the 1940's.
If you have to ask, take that nice original pair of sissors to a pro for sharpening the first time. After that just take a small kitchen steel and run it down the angled edge several times following the angle exactly. Do not touch any other part of the blade. No open and close them, they should feel rough. open and close them several times till the roughness goes away and they are ready to use.
My cheap Fiskars will cut you bad if you are not careful and they are 5 years ols and have been used on leather. I don't recomend this except on very light leather because the last pair got the plastic handles broken that way. I caught heck from my wife and bought my own durned sissors.