Replacement gears for Chester Champion 20V mill

[CharlieRam]

So it appears I have overworked my Champion 20v mill, the main plastic drive gear has lost all but about 5 teeth! I was using a fly cutter set at 60mm with 0.5mm depth cut and approx 200mm/min feed (just over one rev of handwheel per second ish!), Is that too much for a hobby mill? I was milling a 60mm wide channel in one of my alu plates and got to about 8mm deep. TBH it did sound a bit rougher than when I used my mill the last time to do another channel which went fine so maybe the gear was on it's way before it mangled. Cutter was just reground and was nice and sharp.
Anyway I have ordered a new top gear which took longer to order than it should but I have since noticed that one of the inner gears (low) is also missing a few teeth and I'm wondering if it is possible or advisable to get metal replacement gears and if so, where from? I also wasn't too pleased that I had to pay for the replacement gear as I only had the machine for 7 months, I understand that it could be down to abuse but I would of thought .5mm depth in alu on 60mm diameter would be easily achievable?

Cheers, Charlie