Lunchbox that keeps food warm

My 18 month old goes to daycare twice a week he has a lot of allergies and can’t eat any of the lunches they provide so I pack his lunch for him. The problem is he doesn’t seem to like his food cold and I’ve been dropping off a fresh lunch 15 mins before lunch time. This isn’t something I can keep up, but I haven’t found a lunch box that will keep his food warm. I have bought a thermos and send that apart from his normal lunch box stuff but it’s just a lot of containers and I feel bad at how much help he needs with just setting up his lunch.