Selway, sawtooth or a pintler on sale. $350 is a good price. Mule, crewcab, etc are also cheap. Seek outside and a few other names make some cheaper packs too.
Another route is to get a frame with a load shelf. Clip / rig a day pack to it and you have the same function for a lot less $$.
I have and use a pop up as a day pack that can haul in a pinch. It will do 50-60# but it isn’t pleasant. It just doesn’t have the rigidity of the frame Or the belt and shoulder straps of a full size hauler. Unless I was going ultra light I wouldn’t use it for overnights. 28 liters fills up quick. I even go with a sawtooth for day hunting later in the season When I am hauling layers day hunting.
Rumor has it MR has a 40 liter bag for the pop up but it still wouldn’t solve the frame issue.