If you need to sleeve a 26.0 bar to a 26.4mm stem, you will need a 0.2mm shim which is approximately 0.008"; IIRC a beer/soda can is about 0.003" to 0.005" on the sides. Many hardware and big box stores have a K&S Metals display which likely has the correct shim stock. If not, a local machine shop (you only need a small piece) or McMaster-Carr should be able to help.