You may find one that fits (mechanically) but the result, as Canuck mentioned, would be an awfully slow lens and probably soft images.

That Tamron is an f/6.3 wide open at 300mm. So if you get a 2x TC, it would be an f/13 lens wide open at 600mm - darker than many spotting scopes.

If you want to start wildlife slow and inexpensively, I would suggest getting a good/fast prime like a 200mm f/2.8 or 300mm f/4 coupled to a 2x TC. Or if you can spring a little more cash, a 400mm like an f/5.6. Zooms for wildlife don't make much sense to me. You'll always be using it at the extremes anyway.

Good shooting :thumbsup: