I think the ones from the sports shops would be a bit better quality than the kmart/target/big w kind of ones. But then it depends how much you are going to use it. If you're like me and intend on giving the thing a smashing every day for many years, then spend a bit extra money. But if it's only going to be every so often, then maybe a cheaper one could be alright.
The other thing is to make sure that you are comfortable on it.... ergonomics wise. If it feels good to use, you'll get on it a lot more often