Reddit reviews M-Wave Bicycle Safety Reflective Pant Leg Band

These plus judo lessons, to learn how to fall without stiff-arming.

As others noted, there's no reason for your shoes or socks to touch the chain - so that's just a technique and control issue you need to work on.

However, chainguards are very helpful and don't typically require bolt holes etc., on the frame. However, some require you to remove the bottom bracket, which requires specialist tools and 20 minutes. e.g. this from Velo Orange is pretty smart.

Only a chainguard will protect pant/trouser legs though, short of rolling them up, tucking in socks (ruins socks), or getting clips - I like this style.