About 8 years ago, I had the same problem...2 blown M260's (cons. serial #'s, no less), and the only option was to send them to Beyer. I got the mics for free, so I could justify the 210.00 (!) each that Beyer charged...they are now wonderful mics, and I use them all the time...
But now, the Sank mod is the cheese, IMHO...
1/2 the price, and, although I haven't heard
the M260 mod (I *do* have an M500 and a B&O that Stephen modded--both are great mics), this is the way to go...
Just do it...you'll love having those mics around for female vox, drum overheads, amp cabs, etc. etc...
Get a couple old Ampex 350 tape recorder electronics or a couple old
Altec 1567a's, or anything with a *lot* of gain...it's a great combo...
Bruce Harvie
The "Mandolin Graffiti" liner notes are at:
http://www.bruceharvie.com