Just ran into the same problem on my 02. Wife insists that the Front passenger seat and floor area is a grocery tote. Something snapped the right hand mount clip off. Go find a 98 and up and pull out the ashtray . On the sides of the cavity are 2 clips that have tabs to mount them to the cavity. One end has a post (upper slide) and the other has a circle like a small wheel (bottom mount). Pry off and snap into the cavity on the side affected on yours. The post end goes on top. Best to replace both.
2002 S-10 ZR-5 Quad-CAB
1995 GMC Jimmy 4Dr. SLT