...or
here. Personally I'm leaning more towards this; haven't heard/read such good things about the dual sim adapters. From my understanding of it, although you have 2 sim cards in your phone using the adapter, you are only able to use one at a time, switching to the other as/when required.
By contrast with the dual sim card phones, both sims are simultaneously available via duplicated circuitry. Given that all the dual sim phones on the market are supplied standard with 2 batteries, I have my suspicions that they may be a bit fond of their tucker. Despite that, it seems a better proposition to me as I currently have to carry 2 phones -1 work, 1 personal, as I suspect possibly many others do too. Having both available simultaneously in the one handset is a fairly major advantage IMO. Maybe not so important in the situation you describe though.