Class pets

I received the petco pets in the classroom grant. This grant gave me a hermit crab kit and two hermits. I was under the impression that the kit included everything they needed. I have since learned that this couldn’t be more wrong. I got a free 30 gallon tank that I will be switching them into. I’m going to buy a fifty pound bag of play sand and mix it with a brick of coconut dirt. I also am switching out the water bowls for deeper Tupperware. I ordered a heat mat that will be here tomorrow. Now here’s where I need help, because this was a grant I wasn’t prepared to spend lots of money getting their home set up. I have already blown past my budget with just the heat pad and the temperature/humidity monitors. I know I still need enrichment items and that I should switch the pellet food out. I know I also need lots more shells. Any budget friendly ideas on where to get these things? Or know of a store that might be willing to donate it to the classroom? I really want Hermie and Hermen to have the proper home, I just wasn’t financially prepared for how much this was going to cost. Thank you for helping out a teacher who is in over her head and her class who already loves their new friends. I have attached pictures of their current set up in the hermit crab kit.