This 16mm slider system with open linear ball bearing allows you to easily build axes ready for accurate movement under heavy load. The system consists of the sliding block and sliding rails, sold separately. Using short M5 screws the SBR16UU allows for easy solid mounting.
Together, 4 sliding blocks and two sliding rails will work great for your heated bed movement. Additionally can also purchase the MDF heated bed plate to have a complete solution. Note that you want spacing between the heated bed and MDF plate as heat of the bed will evaporate gases from the glue in the MDF plate.
Of course, you can also use the SBR16UU in linear movement of the other axis. Mounting two sliding blocks a few centimeters apart will allow for vertical movement as well.