We realize this may be hard for some stores, if you're working from home or don't have an actual office. Luckily the CAN-SPAM act simply requires that the address you include be one where you can receive physical mail from customers.
Here are a few alternative addresses you can use in your footer if you don't have an office and don't want to put your home address:
PO Box - they can cost as little as $5/month and are simple way to get an address for your email footers.
Distributors or Store Affiliations - if you're affiliated or work closely with a retail store or one of your distributors, you can ask if they can receive mail for you.
Your Work Address - if running your store isn't your day job, you can ask your employer if they are okay with you receiving mail at their address.
A Friend's Business - if you have a friend that can receive mail for you at their office or shop location, you can use their address as long as they can reliably get your mail to you.
UPS Stores - UPS stores offer PO Boxes with the PO Box address. You simply use their physical address and a 'suite #' and they'll forward your mail to you.
Co-working Space - Working alone at home everyday can get boring! Rent a desk at a local co-working space, use their address, and make some friends in the process.