The dimensions are important.
I ideally would like a range :
Radius from 25mm to 35 mm
Cut Height 10mm to 15 mm
Let me explain exactly what I am doing. I am trying to make a double reed for a musical instrument from seasoned cane, usually arundo donax. The outside diameter of the cane varies from 18mm to 26mm. To make the reed, the cane is cut into lenghts, usually 110mm long. I then split the cane to get the required size e.g. 14mm wide. Each side is sanded/planed to get an exact consistent width along the length of the strip. The cane is then gouged on the inside to remove surplus material. It is then finished on a curved sanding block of desired radius. You end up with a strip with the centre being 1mm to 2mm thick, and the edge being sharp. I can then begin to build the reed from this strip. Using this technique I find it very difficult to get consistent thickness along the length of the strip, so I thought that if I used a router I might improve my accuracy.
Lee Valley has one that is very close to what you want. Item 16J29.58, 1 3/8" x 5/8" (34.925 x 15.875). $33C. I have a number of their bits and find them to be a good compromise between quality and price, i.e., not quite top of the line but very good and moderately priced.
Cheers JoeWalsh, I am afraid you are looking for something impossible; such a wide bit (diam.70mm), will not work on a router at 18-22,000 rpm, whether the shaft be 1/2" or 1/4". The energy it will accumulate from rotation (called rotational inertia I think) and the tension it will create on the shaft as it moves and bites its way sideways, will either burn your motor or break off the bit suddenly and it will fly over to whatever it hits first. with instruments working at these speeds, you are required to play it safe if your integrity is more important than the job. This is the reason why very often you don't see the awkward bit you need - it wouldn't work or wouldn't be safe.
Again I did not quite understand what you are trying to do with cane - cane? what size cane would need a 70mm bit? A diagram would be very helpful, but then it maybe my English - forgive the ignorance.
At least let us see a finished job, even by someone else.
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