I wasn't going to add the counter to mine either, mostly because the E-11 that Luke and Han use in ANH doesn't have the counter. I'd rather have Luke Skywalkers E-11 than just some stormtrooper blaster.
I thought the same first when I got my Sterling which was particularly designed to be the one in Hans' hands when shooting in the Detention Block. But after adding the genuine Eagle Hengstler and the PWC cylinders it all changed, the blaster looked so much better. I can easily return it to the original look since the counter is removable.
I used e6000 aon some parts and loctite super glue on others. The only thing that had a pin was the charging handle and selector switch but I did use screws on the grip, stock, and scope
It's made from a piece of aluminum flat, then I bent it, drilled the holes, and cut the notch out. You can get them at Home Depot, Lowes, and most hardware stores.