“On the cheap” & Kifaru or Seek Outside don’t really go together that well.

The Eberlestock F1 Mainframe

https://www.midwayusa.com/product/2634132812/eberlestock-f1-mainframe-backpack

& superspike duffel

https://www.midwayusa.com/product/2634358938/eberlestock-super-spike-duffel-bag-nylon

Have served me very nicely tho I don’t know how much better they’d be than the external frame you already have?