As the others have indicated, there is no need to purchase LM90-30 software. You can download it from the GE Fanuc support website.
The next question is, why LM90? It's an obselete, DOS-based package. You may be able to get it to run and to communicate with your PLC under the latest Microsoft operating systems, but you should expect problems.
If you are going to purchase anything, purchase Cimplicity Machine Edition Logic Developer PLC. Part number IC646MPS001, list price $800 US. You'll need a computer with at least a 500 mHz pentium-class CPU and 128 meg of RAM. (They recommend 1 GHz and 256 meg) If that's not available, then purchase VersaPro, part number IC641VPS300, list price $800 US. Note that the sales people are going to promote CME, and for good reason. It's the package that will be supported into the future. As new products are introduced, they will only be supported by CME. The only reason to buy any package other than CME is if you don't have enough computer to run it on.
When I did the 'Where to buy' thing on the GE website, Barbados wasn't a choice, but I entered 'Caribbean Islands' and got the following contact, which looks like the Miami sales office.
GE Industrial Systems
Telephone: 1-305-551-5177
Fax: 1-305-551-5129