if you want to just use alkalines, I think the Princeton Tec EOS is your best bet under $50. it has a nice, smooth beam that's great for the outdoors. it's reliable, is regulated, and has reasonable runtimes on alkalines. should be able to find the latest 70 lumen model for around $35 on brightguy.com.
if you want to use 123s, there aren't that many options for under $50. Streamlight Argo HP uses 2 123s, is built like a tank, and costs about $30, but the beam's tiny hotspot limits its usefulness. Princeton Tec Remix Pro uses a single 123 and costs about $50, but if you're gonna spend $50 for a Remix Pro, you might as well spend $14 more and get a Zebra H31w. the Zebra is very nice and very versatile