I recon that a 4x MJF6388 and 4x MJF6668 (10A Darlington pairs) could be pressed into service. they are current, available from [link=http://www.farnell.com/]Farnell[/link], and have an electrically isolated tab for easy heat sink attachment. Once time permits, in the next week or so I'll order some, knock up a a circuit on strip board and report back.

Yours Simon M.