[janoskiss (Steve H)]

Stick it in a barlow and the BV should work in your 10". A long barlow would be better than a shorty. And if you have/get a basic GSO 1.25" barlow (or similar), the achro lens assembly that unscrews from the bottom of the barrel is what BV sellers often call an OCA.

If you do get an OCA and still cannot reach focus, get an extension tube to go between your BV & OCA. This will boost the magnification and give you more room for reaching focus.

If you want to BV widefield / low power, that is just not going to work very well. Yes, it is doable, but it will not make use of the full aperture of the scope. It is a fundamental limitation on the geometry of this type of setup. In practical terms, your usable BV-ing FOV in a 10" Dob will be limited to what you get monoviewing with <20mm plossls.

Re astro dealers around Adelaide - give Matt from telescopes and astronomy a call. Do not be put off by the hideous website. Just talk to him and tell him what you're after. He's a straight up and cluey astro gear dealer in my limited experience. (If he's still in the biz. It's been a few years since I dealt with him.)