Low step-ups are a decent, not perfect, alternative. I could've sworn I stole the idea from Ben Bruno, but I can't find the video right now.
Basically use an aerobic step or anything similarly short and sturdy, so you're not quite marching in place but are actually doing high rep/low height step-ups. I've even used the first rung of a short step-ladder for this and it's been fine as a short-term substitute.
This is always a good option too.