Hi there,
Just confirm which type of fitment you have currently, it changed from boot type to clip type somewhere in 1992 but you never know. If they just press on it's the earlier version, if there's some fiddly grey clips involved it'll be the later one.
The genuine part number for a boot type set is 90919-21488
The clip type has two different parts numbers 90919-21540 & 90919-21587 listed but I'd stick with the second one.
If you can't find a helpful Toyota parts dept there's a few aftermarket equivalents available. Look for Magnecor, NGK and Ultra brands advertised as upgrades but remember to buy the right version (boot/clip). The likes of RHDJapan or Nengun should be able to supply them if you don't have a distributer locally.
Hope that helps,
Jay