Go ahead and start looking for another kitten. It WILL help you cope. When mine passed, I had to immediately find another one because his brother started going crazy. He would look for him everywhere and became extremely clingy and would moan/cry all day and night. He wouldn't leave my side. I figured while he'd know it wasn't his brother, he'd still find comfort in another cat.
So within the month, I was able to get him a little 8 week old female kitten playmate. At first, he was like "who the fuck are you?". He'd just sniff her and kept patting her head. Like "get the fuck away from me"
But within a month, they started getting along really well. They're now inseparable and it definitely helped me and him cope through the loss. You can tell they love each other. If I seperate them, they immediately start freaking out.
Also, I wouldn't be surprised if the mother cat is pregnant again. They usually give birth in March/April, then again in June/July, and depending on the region, again around September/October, though those usually don't survive because of the winter. She could have even given birth already and is hiding them. They're very crafty in how well they can hide their babies. Just don't take them from her before 8 weeks.
Completely off topic, but Infinity weren't you the one who had a kitten with a wound on her belly (possibly by mother)? If so how many of them did you keep?