I'm so sorry to hear about the loss of your cat.
I've seen cats dry nurse (suckle) for 2 reasons - they are stressed and trying to comfort themselves (it sounds like your Kaleb may fall into this category), or when they are simply very content and relaxed. The cats that tend to do it more than others are those that were separated from their mom at an early age. If Kaleb has been at a shelter since he was 4 weeks old, I suspect he didn't have a normal bonding time with his mom. No mom, stressed by living at a shelter could very well trigger his behavior right now. Suckling is a natural behavior. Doing it so long and as an older kitten tells me there is something going on with him.
Some people have success with Snuggle Kitties
. Humane Societies specifically use these when they have orphaned or abandoned kittens to bring them comfort. He may be an older kitten and not respond quite like a youngster, but it might help you.
You may try a lot of interaction with him to distract him from his need to suckle. Play with him as often as possible to tire him out. Snuggle with him, and keep something soft (tshirt, towel, etc) that doesn't shred for him to suckle on rather than on you. As he matures and gains confidence in your home, his need to suckle will slow down and hopefully eventually stop.
You can get a kitten bottle from a vet if you like, but this is a behavior you should try to redirect to something more positive, rather than reinforcing it. If you reinforce it, he may never kick the habit.