Aloha aloha,
for specialty tennis, check out Waipahu Tennis Raquet
www.yelp.com/biz/waipahu-racquet-surf-and-sports-honolulu. a bit hard to find... on King Street, after you pass Washington Middle School, and then Zippy's, slow down, it will be about 20 yards on your right. On the 2nd floor above a bar.
in the area is McCully Bicycle & Sporting Goods
www.yelp.com/biz/mccully-bicycle-and-sporting-goods-honolulu-2. They have a good variety to include tennis/basketball/diving/fishing.
for other sports like football/soccer/wrestling/jujitsu (or just to check out a local sporting shop) take a look at Cardinal Sports
www.yelp.com/biz/cardinal-sports-honolulu
while you are in the neighborhood, might as well stop by Soccer Locker, which is just a couple blocks away on Kapahulu Ave
www.yelp.com/biz/soccer-locker-and-sports-honolulu