Umarex makes a fold-down sight that pins the same way. I think the best solution is to get the $20 clamp-on gas-block/quad-rail and the rail-mounted sight (also about $20, I think). This arrangement covers the ugly holes, and gives you the option to use a multitude of sights, bipods, lasers, etc. Most come on and off with just a thumbscrew. Also, it has a place for the original sling swivel. I believe acompany called UTG makes this stuff.