Should have clamps that take earless pliers to remove, have heard of people using ty-wraps in a pinch, dont know how well they will hold, is the grease coming out of boots? If so you need to put grease in them then re-seal.
I used a zip tie while out on the trail one time. If you have the thicker, heavy duty ones it worked for me. They dont have any pressure on them they are just holding the boot tight so I think it would work for a quick fix. The farm store also sells metal zip ties, however they dont seem to hold up as well as the regular plastic ones.