Well, you need to replace the broken part.... (grin)
Seriously, the plastic shifter bases have been known to break, especially with "over enthusiastic" shifting. Some models had a metal base (SVT?), but I can't remember right now which ones... Try a search for "shifter base" & check the "stickies"...
For now, the zip tie suggestion, or maybe Baling wire for a more secure tie down might get you by until you can do a "proper" repair....