I would take a block of allum. and machine something like this...
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does this make sense ( beam enters from left, jogs down, exits right) It is a 45 degree slot machined in a block and a mirror mounted on each face..i used to make these for the big yags...i called them beam joggers..hope the drawing makes sense.
OH CRAP...when i hit return it screwed up the drawing...sorry....
looks goood before i post
Pat B
laserman532 on ebay
Been there, done that, got the t-shirt & selling it in a garage sale.