They can be purchased from overseas, BUT... I know that in the US of A a phytosanitary certificate is required to ship Tillandsia internationally (US Dept. of Agriculture has raised the fees for that certificate to $62.00). Then you have to take a few other "red-tape-headaches" into consideration, such as: specific customs requirements, import permits if required, and how fast you want it shipped. Also, most sellers are not able to insure international shipments. If the plant is on the CITES list, more hoops & hurdles (regardless of whether or not the plant is from the wild, or commercially grown/propagated).
It's not really worth it on the buyer's end, and is definitely a 'case of Tylenol' headache on the seller's end.
You might want to check out www.bromeliadforum.za.net
(several Australian Tilly growers post on the site). You have to be a registered member to post, registration is free though. Once registered, you could post in the Tillansioideae section and/or Resources section. If you go to www.bsi.org/brom-info/sources_int.html
you will find names, addresses, and phone numbers of several Tilly growers located throughout Queensland, New South Wales, & Victoria.