IP Blocking

[whatever]

I have an Australian web site that is being visited by visitors from other countries. Overseas visitors are of no use as all sales are retail through a fancy dress/costume store. Visitors from the USA make up about 70% of my bandwidth which is a waste of 10GB.
I know I can block IPs by country (htaccess) but this will also block search engine spiders and bots.
My questions are: Is there a better way of blocking overseas visitors and still allow search engine access? Or, how can I identify IPs search engine bots and spiders and allow them in my htaccess file? Thank you.

[incrediblehelp]

Have you tried the geo-targeting in Google Webmaster Tools?

[whatever]

Thank you. I will give it a try.

[Tech Manager]

You could also just as easily setup an .htaccess list to only allow Australian IP Blocks.