This instructable shows how to make an adapter in order to move your bike computer or the likes from the handlebar to the stem. I needed to do it because I run out of room on the handlebar, and it worked fine!
1) 1x wine cork (can be actual cork of silicone, perhaps another material - desirably lightweight and easy to work)
2) 1x tie-wrap (make sure the tie-wrap is long enough to accommodate the mount, the cork and the stem as in the image. 3) The existing handlebar mount for your bike computer/lamp/etc.
Step 1: Cutouts for tie-wrap on plastic computer mount
You can carry out these cutouts in a number of ways. I did it by drilling two 2mm diameter holes using a handheld portable drilling machine, and removing the material in between using a Stanley knife.
Carry out one cutout on each side of the mount.
Step 3: File out grooves on the cork
On these images you'll see grooves filed out on the cork. The thin grooves serve as guides for the tie-wrap and help the mechanical stability of the whole thing.
The large curved groove carved out of the cork will fit the stem. CAUTION!! --> The groove fitting the stem NEEDS TO CORRESPOND to your preferred final position of the computer/lamp/etc. Thus FIRST OF ALL think about it, do a mock-up and determine what's the position and angle of this groove in relation with the thin grooves for the tie-wrap.
Step 5: Place the mount+cork on the stem
OPTION: piece of rubber between stem and cork, possibly between cork and mount too. I didn't use it and it worked fine, but could also be useful to keep it in place without a large tie-wrap tension.
NOTE: You may need to use a pair of pliers in order to pull the tie-wrap to the required tension. CAUTION!!! --> Some computer mounts may not be very sturdy (e.g. those purchased separately when the original mount is missing)... those will suffer from undesired bending under the tension of the tie-wrap, compromising the electric contacts between the computer and the mount. My advice is to find a compromise between tie-wrap tension and mount deformation. Enjoy!