Using the isobutane/propane 80/20% mix shouldn't damage the lighter or cause any safty issues but it would probably be a good idea to discharge the lighter during the summer months and use normal butane and only use the isobutane/propane mix during the winter months if using a cheap chinese made butane lighter. Brunton and Primus both produce fuel tools which are specifically used for these commercial gas canisters that have an even higher propane percentage of 30% so their own lighters shouldn't really have a problem using the isobutane/propane 80/20 mixture such as the cannister produced by MSR.

If you find that a flint ignition lighter rather than a piezo-electric lighter is preferrable then the Zippo BLU gas lighters look the business.

http://www.zippo.com/Products/Zippo_Blu_Lighters.aspx?bhcp=1