Have you priced the springs up at Amayama? I'm buying stuff all the time from them. True, you can cop for some import duty but it's still way cheaper than Toyota UK.
Years ago I replaced all 4 springs on my first 80 with OEM ones which then worked out at £660.00. It transformed the ride to like new. I'd had it from 2 years old and replaced the springs at 15 years old.
I wonder why the springs need changing, our 120 has done 175K and still has pretty much the original ride height and drives very well. That said, it has only been loaded up a few times to 500kg.