something similar to zip ties? (heavy duty)
250lb cable ties are made, yes. "industrial zip ties" seemed to be a pretty good search string for finding sources.

Probably more the cold making the plastic brittle than the basic strength of the zip tie. They do make "large, industrial" zip ties (I've seen 3 feet long and half an inch wide, and they probably go bigger) but you'll probably get better cost and service from rope, and learning to tie a "trucker's hitch."