you can get the shims bout anywhere toyota, off used heads sh!t even amazon the 25mm shim comes in sizes i believe 2.30-3.20 anything smaller than 2.30 and you may have to make the adjustment from the top of the valve i wouldn't recommend using my method that i stated earlier in this tread but it does work just make sure you use very fine grit sandpaper so when you do get the desired size that its nice and smooth and almost polished we did my buddies 7m with old shims from another head, reused some existing shims in diff spots sanded a few and bought a few sounds like a pain but these shims start to add up fast and were on a budget almost 5000 miles on his valve job and still sounds nice and smooth
you should also be able to find the shims at a local motorsports store they used those shims in bikes too