There is no shortage of stands along the beaches to sell tourists swimwear, sunglasses and other assorted knick-knacks. Main Street features a wide variety of shops and galleries. Cherry Lane Mall has pretty much everything tourists and locals need for their day to day; national upscale retailer The Bay is here. Penticton also has a few big-block stores such as Walmart, London Drugs, Staples, etc. These can all be found by driving along Main Street. If you reach the other lake, you've gone too far!
For the literary crowd, Penticton features the 5000 square foot Book Shop 242 Main Street, 492-6661 (http://www.bookspenticton.com/). This massive store stocks new, used and out of print/rare books on any conceivable topic, including a large section on local interest.
For traditional local gifts/souvenirs you can visit:
Pennyfarthing
310 main street, +1 250 493-2622.
Terwilligar's and We R Unique
Two for one! 675 main street.
Dragon's Den
12 front street, +1 250 492-3011.
For a more meaningful, intoxicating, or just plain tastier souvenir visit one of the area's many wineries, and one of the many fruit stands dotted along the highway and backroads that sell local products.