I've seen Melophorus bagoti queens for sale on Queen of Ants- The Best in Australian Ants, Available Worldwide and The Ant Lab . They usually come in stock around February each year, but are very popular and usually sell out within a few days.
You'll likely need to travel to Australia to receive a queen from either of these companies.
(Also, if anyone else is selling them (in Australia) $175 or under you have yourself a deal.)
ZTYguy, ColAnt735 and pcp like this
Colonies: Camponotus humilior 1w, Opisthopsis rufithorax 11w, Aphaenogaster longiceps ~5w, Pheidole sp. ~235w ~15m, Iridomyrmex sp. 2q 1w, Brachyponera lutea 6w, Crematogaster sp. ~20w, Podomyrma sp. 1w
Queens: Polyrhachis cf. robinsoni, Polyrhachis (Campomyrma) sp. (likely infertile)
Previously Kept: Colobopsis gasseri, Technomyrmex sp., Rhytidoponera victorae, Nylanderia cf. rosae, Myrmecia brevinoda/forficata, Polyrhachis australis, Solenopsis/Monomorium
Key: Q = Queen, W = Worker, M = Major
Youtube Channel: Ants of Sydney - YouTube
Patreon (for YouTube channel): https://www.patreon.com/antsofsydney