Non-magnified? Tube, or reflex?
For non-magnified airsoft purposes, I get on fine with this style, which is sold in many many rebrandings from Amazon, eBay or AliExpress. I have two. They're light but solidly enough made, hold their zero over a day, are bright, and have a variety of reticules. Importantly, they're cheap enough not to cry over if you run without a sight protector and they get shot out. I really can't justify paying more than £20-£30 for a sight that's more consistent than the BB.
What don't you like about your current sight?