Talk to the guys at empeg. Last I heard anything about MkI panels they had plenty left... You'd need to drill a hole for the knob axle and either get the MkI style buttons or machine the button holes to fit the MkII style buttons.
For that operation I'd talk to DarkStorm, who could probably also set you up with a custom color MkI style panel fitting a MkII or machine a MkI panel to fit a MKII, as he's the guy that has been making custom color panels both for MkIs and IIs...

/Michael