I wouldnt think all those stores have a 250D/296D serial cable (the end on the scanner side is the different side)
If it was a base unit 785D 796D a standard 9pin would work but the handhelds are tricky to find
try unidendirect
Call 1-800-297-1023 for Uniden Direct Special Orders
it looks to be discontinued from everywhere else
its a pretty hard to find cable. part # RC250D (least from usascan)
Radio Shack, Wal-Mart, Staples, Office Depot, eBay.... assuming that your PC has a 9 pin serial com port on it.