What a great gesture. I wish you the best of luck. Here's some ideas, hope it helps.

You can hold bake sales, hot dog sales, candy sales, or pretty much any food sales, car washes, garage sales, eating contests, can/bottle collection, or you can put collection cans around at local stores.

Hand out & hang up fliers around town asking for donations/items.

Also if you have any fairs or the like you can do booths, like face painting, craft sales or contests, food sales/contests. If there is a chaarge for a space/booth ask the people in charge and explain your situation they may donate a space for you.

If they need supplies you can put flyers up or see if you can mail flyers to everyone (I think it's called bulk mail or something) asking for items/foods and have a food drive type thing, or you can post a location for people to drop them off.