My granddaughter's bed has those wooden slats on her bed frame. While she's been with me, they've come off several times and a few have broken. I need to find something to replace them with. I've had a look around the place but nothing jumps out as being any use. So then I looked online for wooden planks.
My son's twin bed had similar slats and he broke several of them. We bought a piece of plywood to replace the entire thing, just cutting it to size. If you don't have access to the proper tools to cut it down, Home Depot or Lowe's can do it for you. It's very sturdy and has been holding up well for years. It's in our guest room now.
Good luck!
Jess has a good idea but Lowe's or Home Depot will also cut sturdier slats that should hold up better than what you have.
I'm only mentioning this just in case you do not have someone around that can handle a large piece of plywood (like me).
It would be a good idea to measure the slats you have, so you can tell the salesperson what size you need (not all twin beds are exactly the same).
Be sure to notice if they fit snugly or if they could be just a little bit longer.
I believe you can take your measurements to one of these stores and ask for help in finding what will work best for you.
thankyou both of you,i will have to visit one of these places and have a look round!thankyou both so much! xx