THe metric closest to it is 12mm .036 larger than a 15/32. NOrseman is probabaly the best brand for a drill bit they are usa made. At least one of the vendors sell them.
Also put a micrometer on the tubes and see what they measure you may need a smaller drill bit. I have uploaded the pdf of the drill bit sizes and conversions from the library. I heartily recomend saving a copy to your desktop. I use mine all the time.