You might consider getting a slightly larger
winch (e.g., a #10 or #12) as a replacement. Normally one doesn't have to worry too much about the size of a main halyard
winch, as the luff tension is usually controlled via the Cunningham/downhaul anyway. However, since you are replacing the
winch, and since the #7 didn't appear to up to the job, upgrading a step or two will give you a slightly more robust piece of hardware and make raising the main that much easier.
I can't tell where you're located, but if you are in Southern California you might want to try Minney's Yacht Surplus in Newport Beach. They have two or three shelves full of used
winches. Otherwise, eBay (as mentioned above) or CraigsList (a long shot, but ya' never know) are worth keeping an eye on.