It's nearly November- I dpnt think buying a Walmart bike is a great idea because it'll be winter soon so you probably wouldn't get much use before you want to hang up the bike.
Just a guess.
Ebay, Facebook, Craigslist, pro's closet- all are good places to search for used.
The most important thing is that it fits properly. After that, consider component condition.
If a 56 fits...
https://www.jensonusa.com/Marin-Nica...RoCPL8QAvD_BwE
Another common recommended sub $1k bike...
https://www.statebicycle.com/collect...rown-650b-700c
or
https://www.statebicycle.com/collect...nyon-650b-700c
Salsa Journeyman is still under $1k. Jamis used to have a Renegade for under $1k, but no longer. This last year has bumped bike prices up 10-20%.