Plenty of good suggestions above .

I park overnight at Walmarts regularly. I go in and buy a couple supplies then find someone in the customer service area or manager and ask if it's ok. Never been denied except once in 6 years.

For Walmart I find the truck route on Google maps and use it usually. It's usually wider and plenty of room on the apron

For the future I would not ride another mile with that trainer until I had enough supplies to cover for this type situation in the future. I'm not going hungry.

Other great places to eat and park. Don't forget grocery stores are are serviced by big trucks so there's plenty of room in grocery store parking lots. Also, on the peripheral of grocery store parking lots, usually there's plenty of restaurants. And grocery stores will often have no problem with you parking beside them overnight. Again, I go in and buy something and then find a manager. Easy peasy.

Lowe's and home Depot. Also are truck friendly. The only problem with them is you really need to zoom in on Google maps and make sure the parking lot's not loaded with concrete barriers that impede your maneuverability. But the truck Lanes are usually not a problem. Just be creative.

For the long-term future, you might want to consider meal prep. There's enough room in a truck, especially if there's a built-in refrigerator that you can keep plenty of food. I go for a week at a time and never spend money on food in restaurants or truck stops particularly. But that's more about health for me than money. I just don't put garbage in my mouth.

Good luck with your career