I would recommend never touching your 401(K) unless you are retired and using it for its intended purpose. You'll get it with penalty's and have to pay taxes on that money if you don't. With that said you could also try looking at some peer lending clubs for a loan. For example, http://www.lendingclub.com/
is one I've heard of that will loan you money. I would consider talking to a financial advisor about it though before making the decision to buy the shop and then how to finance it.
Also, your projected ROI could determine the likelihood of a loan as well.