The GRE version with more features, the PSR-800, should be shipping in small quantities to dealers in the next week or so. I would expect the Pro-18 in another month or two. Of course it's up to RadioShack to get it into the system and on the web site first, so I would have your son check the RSU computer for the part number. The radios are built in China, so it could take some time now that both radios have been announced and are through the FCC certification.
It doesn't show on the RadioShack public web site yet, so if you have a part number and a price(something like a P/N #20-xxx) and report it here, it may help others who want to order one. It may also show up as the iScan Digital Trunking Scanner with no model number.
Good luck.