Getting a replacement for that vacuum coupler at the local auto parts store won't be easy (maybe NAPA would have it...probably have to go to a dealer; the part number should be embossed on the piece).
As a temporary fix, you could put a small hose clamp on that...but it still could leak and will continue to split.
I permanently fixed mine with a piece of heavy-walled heat-shrink tubing (like for insulating wire), and some careful passes over an oven burner on low.
At the very least, clean it off with some rubbing alcohol and wrap it up real tight with some electrical tape.
2004 Buick Lesabre Limited, Gran Touring; Bone Stock
1998 Buick Lesabre Limited, Gran Touring; Mods: Poly sway bushings/endlinks, Tru-Cool trans cooler, Thrasher shift kit (med), PLIM, front PEM; Mods in progress: Alot of stuff, but slowly...