So I like to have my bees fly around within a greenhouse. Only thing is having to have a block per solitary bee is kinda annoying especially with cuckoos stealing them. My idea is the Segmented Beehive. The segmented beehive is a hive that is split into 4 compartments. Each comparment will store a solitary bee. These hives do not have the ability to contain wild or hive bees and are not able to generate resources, however they can safely store 4 (or more with an expansion box) solitary bees.

There's the Bamboo Nest which holds 9 solitary bees.