The company PB Swiss makes hex wrenches that are longer than normal and work really well. Not cheap but they are the best in the business. Getting stuck nuts and bolts off with a cheater bar is fine but definitely do NOT use a cheater bar to put them back on (it's easy to strip out threads), use a good quality torque wrench for that. In your case a 16" long piece of the heavier duty 1/2" copper pipe (there's standard and heavy) or galvanized pipe would probably work fine as a cheater bar for bike work.