RPB "Fremont" pannier doesn't fit RapExpand 5 rear rack--any alternatives?

[Berkeleysmith]

RPB staff sold me a Fremont pannier, but I quickly discovered the attachments won't allow it to be mounted far enough back on the rear rack to prevent heel strikes, nor does the bottom clip adjust to a position where it can be attached. The RPB staff at my local shop claimed to not have been aware of this. For grocery runs, I'd really like to have a couple of easily-removed panniers on the back of the bike, rather than attaching a basket or (for my needs) a too-small trunk pack. Have any other Expand 5 owners encountered this problem? Are there other brands or hacks that would work? My Ortlieb Backpackers are too large.

[Ishy]

I'm having pannier issues too.  I need quick release everything so it doesn't walk away when I need to lick it up.

As such.  Instead of spending big $$$.  I'm making my own with black Ikea Desk pads($3.99CAD).   I will be experimenting with  Cosplay Costume Plastic that can be microwaved and shaped to make a clip.
   
Construction of the bags themselves will be interesting.   I am planning to use a Cheap Canadian Tire pannier set from Raleigh as a shell and the desk pads to give it a better shape as well as a solid foundation to secure the clips to.   

I might splurge and buy 2 clear desk pads to make a panel to protect the bags from the wheel and mud

[Berkeleysmith]

Update: I haven't been able to find panniers that fit the RadExpand 5's rear rack, but this REI "Beyonder" trunk pack attaches securely, is easily removed for carrying, and is large enough to hold 1 bag of groceries (and carry a knapsack while en route to the store). Inexpensive too--less than $30--so this'll be my cargo solution for now: https://bit.ly/45Qnhcz