Shifters now that they are unavailable what can I use? Hey all thanks in advance for help on this matter. 

I have a Diamondback mountain bike that uses shifter set Shimano ST-EF51-8R and ST-EF51-L 3x8 disk brake. Son broke them on a jump, apparently snapped gear shifters off. As Shimano used same model number on two styles of these. I am looking for levers for mechanical disc brakes and 4 finger brake handle (not the 2 finger one). Of course I have been looking for over 6 months bike season is almost here and there has been absolutely nothing available to purchase to replace.
 
so with that said is there a compatible set that I can actually find to purchase online that will work properly no problems decent quality and price? 
​​​​​​​again ty

I am in Windsor Ontario Canada so for now going to Michigan to purchase or possibly pickup an order is out of the question. Unless shipped USPS to canada less customs hassle USPS. 

Ty all with the so much help and understanding in this. I have decided to go seperate brake shifter instead of combo unit. After a lot of help and so much research v brake does work with mechanical disc brakes. It was so confusing with all the reads at the beginning. Ty for the edit to make it more sense lol I'm bad at explaining things properly. Again ty all for the very much appreciated help info and ideas.
You do not need replacement combined shifter and brake units. Those were popular at one time but separate units are the norm now.

So you have two separate issues: Finding compatible brake levers and finding compatible shifters.

As other have said you need V-brake compatible levers for mechanical disc brakes. This should give you a wide choice and the ability to find 4-finger levers.

Literally any Shimano 3x8 shifters will work with your existing derailleurs. The expected sprocket spacing and derailleur actuation ratio (ratio of length of cage pulled to lateral movement of the cage) has remained constant for Shimano MTB drivetrains at 9 rear speeds or less. It would be nice to upgrade from the EF51 shifters but Unfortunately Shimano now only makes 3x8 shifters for their lowest level groupsets, but searching on Ebay might net you some earlier but higher level items.