You can try searching for “福祉” on Google Maps. You should be able to find places that sell wheelchairs. Manual wheelchairs are not very expensive.

Or you can check on Mercari to see if there are any second-hand ones.

If you are traveling in Osaka, I can provide electric wheelchair rentals. The design is very stylish, and I use the same model myself. You can contact me at: 99louyu@gmail.com.