there are a few ok clones around such as acogs, elcans and elcan spectres and they are fixed 4x scopes. these seem to be ok but are made in china to a budget and are imported by companies like nuprol. In my experience I have found that these clones can be a bit on the fragile side.
alternatively there is always the vision king short dot which looks pretty sweet on longer barreled SPRs, mk12s etc and a lot of users seem to recommend them.
have a look at the short dot here.
I hope that helps a little, there are obviously other options out there as well if you just have a Google.