First I rummage thru my collection of brackets from blinkies that have given out and other accessory mounts. That produces something that will work 80% of the time. For the other 20% I start by replacing the bolts with longer bolts. I usually try to use stainless steel since they rust less, and are non-magnetic and less likely to interfer with things like computers. If that doesn't work, you can consider mounting somewhere off the handlebar. Profile Design makes little pegs for that purpose. If you don't mind ugly, you can make one yourself using the cap and neck of a plastic soda bottle and a zip-tie. It will be OK for something light like a computer.