It would be helpful if you edit your profile and enter your location. Australia is a big place and it's hard to offer suggestions as to sources if you are in Darwin and I am searching Sydney...
I am assuming you have the R134 compressor?
SJs list the replacement for the R12 but not for the R134 compressor unless they are selling a locally sourced replacement for the R134, but they usually put that in their price list under the OEM number as a SJs "Special Part".
Just be sure you are looking at the correct part since the two different compressors are DIFFERENT and mount differently.
You should be able to go to a local supplier/service shop and get a standard R12/R134 receiver/drier with o-ring line fittings and one service or test port.
US prices are around $15.00 but Aussie prices are probably close to $30.00. I can see several resellers in the Sydney NSW area but don't know the thread sizes on the lines to search deeper. I am pretty sure you have o-ring fittings and a "switch port" for the Trinary switch. I will look at my spare receiver/drier tomorrow and try to give you more specific part numbers or suggestions.
Look at http://www.ebay.com.au/itm/262476826034
? for an idea and a possible supplier source. I am fairly certain one of the Holden car models used the same receiver/drier that Lotus used.
You may need to carry your part to a supplier so they can match it up with their stock.