Might have to bite the bullet & sew something. Kevlar strap laces in the rear, with velcro adjustments, & a common string lace in front with a knot might do it. The wide toe strap in the $125 version doesn't work with lions.

Any new design requires simultaneously continuing to build the old design, since they're consumable & lions have to get around.  

The old design changed to E6000 adhered shoelace instead of nylon washers for reinforcement.  They worked but were pointless & expensive.

Multiple strands of common nylon string have been easiest on the paws, can be tight enough to not slide down, so worth continuing to try despite being very hard to adjust.  Really need a way to eliminate knots.

 Randy Kreill revealed in a video that he wore socks for most of his sandal experience.    Another swing at the xeroshoes with toesocks managed to go 2 miles without causing blisters, but left them still pretty raw.  Going with common tube socks caused irritation from the toe post.