For the PX4 series with a laser-aimer or white light, I'd look into the Bianchi tactical line; www.bianchi-intl.com .
They sell a SWAT/spec ops version of the well known UM84/M12 holsters that can be fit to frame mounted(1913 type) lasers/white lights.
The only other holsters I've seen are the cheap UTG rigs from www.Cheaperthandirt.com .
These holsters may fit & look cool but the quality is not great.
The UTG holsters may fit your budget though.