Outdoor gear lab.com has reviews, specs on about every bag out there but the hunting specific companies. Great place to start, there are some budget friendly 20 deg bags they say don’t quite make the temp rating, so that should put you in the 30-35 range.
Have a look at wilderness excursions- I picked up a 0*C bag for less than $150cdn. I haven’t been able to try it yet (still too cold for a light bag up here) but I’m impressed with the quality of the build. It’s a their below my wife’s western mountaineering bag, but I don’t think it gives up nearly $300 in performance and quality.
I would just look at the fp rating rather than a particular brand and wouldn’t go below 700fp. I got an alps mountaineering bag on clearance for like $130 or so, 20 degree bad 2.5 lbs with 700fp down and it’s holding up great.
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