You can turn down a section of the stock bar ends in a lathe so that they are 7/8 OD. Not the entire bar end, but just a channel wide enough to allow the clamping portion of the mirror to sit inside. Most competent machine shops can do this for a reasonable fee (probably less than the ~$20 per side the CRG adapters cost). The pic below is from a Ducati, but you want to essentially end up with the same finished product.