My old Airport Express (1st gen) is pining for the fjords...

Anyone have a recommendation for a portable WiFi router/extender - one I can configure in various ways to meet whatever needs I run into?

I'd like to sometimes plug it into an ethernet cable and create a private lan. Sometimes the same via WiFi. Sometimes I'd like to extend an existing lan, via either wifi or wired. I don't really need AC (G/N is fine), but I'd like it to support 2.4 and 5 GHz, ideally with channel bonding in the 5 GHz range - I'm so over misconfigured 2.4 APs messing with me.

Any suggestions?

thanks!