1990 Mazda MPV Question: where & how I can purchase the hydraulic valve lash adjusters?

I am wanting to know how & where I can purchase the Hydraulic Valve Lash Adjusters & a Hydraulic Timing Belt Tensioner for my MPV. I have been hearing a ticking noise from the top part of my engine & I was told that I needed to replace the hydraulic valve lash adjusters but Im having trouble finding them in my local auto parts store. I have also been expierencing loss of power & hearing a loud rumbling noise when I push on the accelerator & was told that I needed to replace my Hydraulic Timing Belt Tensioner. please help!!!!!