Maybe a bike shop?

Don't lots of gas stations or carwashes have a free air pump?

There are pumps on small compressors that should work-- I'd think you'd get one at a sporting goods store or Walmart/Target. A manual bike pump will take much longer (and isn't a whole lot more efficient than blowing) but should work eventually. I'd be concerned/cautious about a gas station air pump.. but that's what I'd use based on convenience and cost.

How about a store where they sell balloons? Of course you don't want it filled with helium, but they may have something for non helium balloons....

There are compressors for water toys, like tubes that are pulled behind boats. There are also foot pumps for things like rafts. What will fit may depend on the valve. Is it like pool tube? Or a bicycle? There are also compressors for inflatable mattresses, but I'm not certain what kind of valve those have. And of course compressors for air tools, but that's probably a little beyond the price you want to spend.

Look for something like this at Target/etc. Maybe even toys r us if you would dare go near any of those stores right now.

This one uses a cig. lighter. They also have ac ones

Here is a link that might be useful: pump