Thank you all so much. After reading the replies I took a search. There is an even cheaper one like the Dajia one
here, however some people seem to have trouble fitting it to certain bikes. My bike has 700c wheels. The Walmart one is foldable, and I found an seemingly identical one at
Amazon, but some also seem to have problem. Guess I have to try one in person to know.
Thanks again for the quick replies.