Shopping with my son

Looking for tips on how to make shopping with a child in a wheelchair easier!

A little backstory: I have a 5 year old and a 2 year. My 5 yo cannot walk long distances, even with a posterior walker - it just wears him out and makes his body hurt. Due to career changes, I am needing to do more physical shopping in the stores to try and find deals/save money. Does anyone have any tips on setups or accessories that could help?