There are many types of rubber mats you can buy to put by his bed to prevent falls.
Here is a link to one website that offers different types of rugs: The rug needs to be non-slip and non-skip.
http://www.easierliving.com/all-products/fall-management/floor-mats
I have also seen similar rugs on Amazon.com – Look for rubber mats that are non-slip and non-skip.
Another idea is to see if your Dad might to able to use a urinal – This is a receptacle he could place near his bed and use it night while he is in bed so he wouldn’t have to get out of bed at night – these can be found on Amazon.com.