Try Bunnings Special Orders. They used to sell the Talon brand.
Alternatively, detach your cutter head and take it in to Bunnings and compare it with the Ozito shredder they're currently selling. It looks like it came out of the same factory as the Talon brand, might be an interchangeable head.

With a lot of those items, sadly, you can find yourself up for an expensive part (and no guarantee) whereas for a few $ more, you can get a complete new unit, with a guarantee. (And your old unit is now rubbish). The head and the blades will be the most expensive part of the tool apart from the motor (maybe).

And while I'm content with my Talon at the price I paid for it and the amount of work I ask of it, I wouldn't buy one again. I'd go for the more expensive grinder-shredder machines, as against something with whirling little blades that are difficult to sharpen. (And easy to cut yourself with!)

Start with Bunnings Special orders. They aren't sold by Bunnings under the same name anymore, but identical items are being sold under different labels.
A quick Google turned up:
https://www.outdoorking.com/chippers-shredders/talon-chipper-parts/talon-ryobi-mcculloch-homelite-chipper-blade-579250001
Which looks like the right part. They also have the weirdo screws at $2.75 ea - probably worth it, $11 for 4 screws. But! - I can't verify that this is a good company, I've never dealt with them.

I have sharpened my old blades on a belt sander - but even with gloves and locking pliers this is very dangerous. And you have to keep them cool, dunk them in water, or the steel loses its tempering; becomes soft.