Good Morning,
I am so very sorry for the loss of little Meeka.
Unfortunately.. It is true freak accidents happen all the time and it was completely out of your control.
It is very depressing for gliders to lose their buddy but it is also very important to try and stay strong for your baby. They sense it just like nerdyhails described..
I lost my baby boy Blue in January, his brother since has not been himself at all.. They change in personality, in effects them as it would us if we had a sibling we spent every single day with..
My mother bought me another suggie joey who has been the sweetest little guy.. They have met through cages and they are currently in the same room.. I won't put them together until they are relatively them same size but I have them slowly getting used to each other until the time is right ..
There is also 30 day quarantine you have to get fecals done at your vet's office etc. before even thinking of putting them together.
As far as getting a joey to go with him.. it takes time
Your doing what you can, spending time with him.. He will begin to change for the better once he has a new buddy as my Nerf (Blue's brother) has been visiting his new brother and saying hellos .. and little by little hes becoming more like his old self very gradual but they grieve like we do just give him as much love as you can !! <3
Again I am so very sorry may your Meeka G.I.P