( CNN ) -- It 's been three weeks since two little girls in Iowa went missing while riding their bicycles near a lake . On Sunday , two cars in the NASCAR Sprint Cup race will sport a special decal bearing the images of the cousins to raise awareness in the case . The beaming faces of Elizabeth Collins , 8 , and Lyric Cook , 10 , will be on the deck lid of cars No . 83 and 93 at the Pennsylvania 400 at Pocono Raceway . A telephone number for the National Center for Missing & Exploited Children will also be on the decal of the two Toyotas , said BK Racing , which owns both cars . `` Being from Iowa , and having some other folks in the sport from Iowa , we 're all pulling together to raise as much attention as possible to help locate the two missing girls , '' said Landon Cassil of Cedar Rapids and driver of No . 83 . `` I really want to do as much as possible and this is one step . '' Travis Kvapil , who drives No . 93 , is a father of three and hopes the team 's efforts will aid in the search . `` As a parent , I want to do anything I can to help the families locate their children , '' he said . Lyric and Elizabeth were last seen by their grandmother on July 13 . Authorities investigating their disappearance believe they are still alive . `` We believe these girls are alive and we are not discouraged by the passage of time since their disappearance , '' FBI spokeswoman Sandy Breault told reporters in Evansdale , Iowa , last month . She declined to discuss exactly what evidence investigators might have that pushed them toward that conclusion . Breault said she believes someone knows something , and she urged anyone with information to step forward . Grandmother : 'We will fight ' A $ 50,000 reward is being offered for information leading to the successful recovery of the girls and the prosecution of the person , or people , responsible , she said . `` Cooperation with law enforcement is the key factor in discovering the whereabouts of Lyric and Elizabeth . Unfortunately , in this case law enforcement has not received total cooperation from all family and close friends . It 's important to note that the majority of the family has cooperated 100 % , '' Breault said . `` We believe there 's someone out there and we would urge them to come forward . '' Family of missing Iowa girls 'bracing for the worst , but hoping for the best ' The girls ' bicycles and a purse were found near Meyers Lake hours after they were reported missing . A search of the 25-acre lake turned up nothing , and the FBI is confident the girls are n't in the lake , said Breault . Authorities are now calling their disappearance an abduction .
Elizabeth and Lyric 's pictures will be on the deck lid of two cars . `` I really want to do as much as possible , '' says Landon Cassil . The girls are last seen on July 13 . ` They were reported missing by their parents at about 3 a.m. when they did not return home from school.