You can get the factory parts or go with an aftermarket kit like this. The slop is usually caused by wear to the 2 plastic cup rings in the center of the picture. This is serviceable from the interior without dropping the transmission. Remove console, shifter, carpet/mat, access panel to get to the top of the trans.
M5R1 M5R2 Shifter Repair Kit Ford Ranger Explorer Sport: eBay Motors (item 360228264578 end time Jun-20-10 09:50:08 PDT)
While you've got it apart, the 3 rubber plugs for the shift rails should also be replaced because they have a nasty habit of falling out, dropping trans fluid and letting dirt/water in. Nothing good could come of that. Use new rubber plugs or get some metal replacements - Internet lore says that Dorman 555-108 plugs are a good fit.