Dunno if it's an intended balance thing or not to have to reset the shop several times when you're mag feeding. Buyable sols 24/7 may be a little overpowered I guess? How about extending the shop list to offer these items always.
People have suggested this or similar a few times. Thing is..there is a restricted limit to how much can be appear. So in order to have certain items be forever in shop other items would have to be taken out.