I think the Nikon Monarch African 1-4X20mm is outstanding, I put one on my AR-15. The very similar Nikon M223 1-4X20mm is the same basic scope, but with a different reticle.
Several other companies make 1-4X20mm scopes... They all seem pretty good, but if I was going to step up from the $280 Nikons, I would go for the Leupold VX-R with the illuminated reticle. I think they go for about $550.