Hi I am an Australian in Vietnam and my Nuvi 205W battery went down. As you can imagine you can not buy a Garmin battery here so I did some researching and found no alternatives on the net. I took the battery out and went looking at the mobile phone shops in town. Found that the Nokia BL-5J is a perfect match. It fits the Nokia 5230 / 5800 / C3-00 / N900 / X6 it has 1320mha and 3.7v. Exact same size and only cost US $3 and re soldering the contacts on the new battery was done for free in the store. Works like a charm.
I hope this helps some else out in the future.

Tim