Mounting Docter to AR15

Does anyone know a good mount to use when installing a Docter red dot to standard picatinney rail? I know LaRue makes one that $150 but theres gotta be a simpler cheaper way to do it. Im looking at using this sight on an AR15 and would like it to co-witness the irons but its not necessary.....

The real deal is $94 MSRP from Doctor.

http://www.docterusa.com/_mgxroot/page_10773.html

You should find it cheaper at other dealers with a Google search.

rc