The stock for the bushing is not likely to be found as 10.5mm material, but can be machined down to the desired size from larger stock. What is the material? Brass? I do not recommend that you use adjustable reamers for that job, they are too fragile and fussy to use in smaller sizes and will not leave a parallel bore to desired size without much care and some luck, especially for a novice. Measure the shaft accurately along it's length and decide the size that you want for the bushing I. D. You will want it snug on the worn pivot area of the shaft while also large enough to slide over the unworn portion. It might make sense to turn down the entire shaft to the smallest current diameter for a better fit and to make installation of the tighter bushing possible. Some of that depends on the layout of the installation, and we do not even know what model carburetor it is. When you know for sure the reamer size you are looking for, you can try to buy one that size. Report back if you need more help. I have lots of reamers, and so do others here, but you are in Thailand, which makes things much more difficult. The bushing could also be made from solid stock, bored to size on a lathe, and then turned to the desired O.D. If there is room to work, the bushings would be best reamed to size after installation in the carburetor. You want the butterfly valve to fit the venturi closely and without binding, and that requires accurate locating of the throttle shaft.
