There are a lot of places where you can buy some bowling balls. First off I would try going to your nearest bowling pro shop because they can help you with buying a ball they fits you and they can drill the ball that fits you as well so I would try that first. There are a lot of online stores where you can buy a bowling ball and I list the 3 top that I use to my bowling balls. Don’t forget that people sell their bowling ball on https://www.ebay.com/ and https://www.facebook.com/marketplace/category/bowling/ and there are cheaper than buying them brand new. If you are just starting out and don’t have a lot of money, you can buy a used bowling ball and sometimes these bowling balls don’t have a lot of games on them. Sometimes people buy a bowling ball and they use for a awhile and they don’t like the ball so they will sell it off the get rig of it. check out my 3 top spots to buy bowling balls:
https://www.cheapbowlingballs.com/
https://www.bowling.com/shopping/all/bowling-balls
https://www.bowlerx.com/resources/best-place-to-buy-bowling-ball.html