I can't help you with the bore guide other than to say that there doesn't seem to be a whole lot out for the 6.5CM when it comes to specialty items. Redding doesn't make an Instant Indicator Comparator. RCBS doesn't even make their Precision Mic in 6.5CM. And that's relatively low cost. Dillon doesn't offer reloading dies...
Hopefully as it gains popularity and a couple more years under its belt more will become available.
Have you tried a generic boreguide for it yet to prove they won't fit?
Barrel length and cartridge/bore diameter really doesn't matter for a bore guide, you just need something that fits the action, then centers and seals into the chamber. I've venture it'd work pretty well with a 308win, 243win, or 7-08 guide tip as long as you find a proper guide that fits your action.