Check out eBay and gumtree, eBay UK is the place for secondhand ST parts,
Some people are happy to post to Australia I have bought a few items from there,
A factor to take into consideration is postage, surface mail can take 3 months or more, whereas airmail
Is faster it costs more. It all depends how fast you need the seat, if you PM me I'll send you
Details how to convert the pod into an opening one.