I'd double check the reptile hides you have, since a lot of decorations for reptiles aren't aquarium safe. If they state that they're ok for aquatic environments, then that's fine.
There are a lot of aquarium decorations that make good hides- hollow logs, hollow stones, buildings, etc. The big thing is to make sure they don't have any sharp spots that could cut or puncture your axolotl's soft skin.
You could also get creative and make your own hides. A lot of people will turn terracotta pots on their sides and just use that. Or get a section of PVC piping that the axolotl can lay in. Even fancier is if you buy slate or large river rocks, and using aquarium silicone, gluing them together to make a rock cave. Again, do a little research on what is aquarium safe- certain stone and wood types aren't safe for axolotls.
Some axolotls even like densely planted areas as hides. My axolotl Motley has one cave-like hide, then a big clump of plants, and more often than not he's hiding behind and around his plants. Or hanging off of them like a goof.
Hopefully this was helpful! Poke around different pet and aquarium stores, maybe even hardware stores, and I'm sure you'll find something suitable for your tank.