How can an EU citizen (Poland) obtain an Australian tourist visa while in Saint Petersburg, Russia?
Is it possible to do without returning to Poland?
Visa applications for Australia can be done completely online! (For Australia)
So firstly, to confirm, yes Polish citizens do need a visa for Australia.
Then, apply for it online. There are sites explaining the whole process.
Australia now does electronic Visas for most tourist Visas, so you will likely be able to apply over the Internet at http://www.immi.gov.au/.
There is no need to have a physical stamp in your passport, and no need send your passport anywhere.