Pedal Platform Adapter Recommendation

[Jimbo]

Hello All:
I am currently involved in a clinical study which involves a cycling rehab protocol. We are using Garmin Vector Pedal based power meters to help the patients improve symmetry in their left/right power balance.
We have been using a rather small pedal platform adapter to allow the patients to use their regular shoes. See the one we use here.
Some of the patients are having trouble keeping their feet on the pedals (these are NOT cyclists!).
So I want to find another platform adapter that is larger and that has a vertical lip on the front so I can mount a toe clip (the kind without a strap).
Can any of you recommend such a platform adapter? Can't find what I want on Amazon. Might have to make my own starting with large aluminum angle but would rather purchase something that's ready-made.
Thanks in advance,
Jim