Some discontinued Merrell cycling/walking shoes had highly reflective heels -- the Roust, Fury and similar high-top and low-top shoes. They glow brightly from the sides and behind, and the reflective material is a mesh pattern that isn't critical about viewing angle.

I have a pair. Very comfy for walking, good grip for platform pedals. Soles are a bit soft and may wear quickly on platforms with metal pins or metal quill pedals. I use them with plastic Stolen Brand Thermalite and Wellgo metal platforms with rubber grips rather than metal pins or sawtooth edges. No problems with premature wear.

I usually carry a few snap-on reflective bands on my bikes. They'll usually hold on my jeans, arm, wherever I need 'em. Two for $1 at the dollar store.

A compact, lightweight Blackburn 2'Fer could probably be rigged to the heel of a shoe, behind the ankle or trouser cuff. A Velcro band could probably hold one. The 2'Fer has red and white modes, flashing and steady, so it's versatile. I've clipped mine onto the back of my hat band, on my belt behind my back, on a saddle bag, pretty much wherever I needed it. Clipped onto collar, shirt pocket or front of a hat, it makes a useful hands-free flashlight for checking paper maps, etc. Before finally getting a proper smart phone with apps I used to carry paper maps, paper bus schedules, etc., and occasionally had to refer to them at night. The little Blackburn 2'Fer got a lot of use for that.

The newer Blackburn 2'Fer XL is brighter and may run longer per charge but is also quite a bit larger and heavier, probably too much for mounting on a shoe. Might be okay rigged to a Velcro or elastic trouser cuff band.