There is very few that sell a mower because it was going too good.
Its hard to get a mower of any sort that hasnt went round the world two or three times tbh.
A tidy one at the right money could be like trying to find false teeth for a hen.
I'm sure there is one out there somewhere but finding it is the one.
for what it's worth, personally I'd never have anything here with an oval disc, stick to round ones, it will serve you better in the long run especially when your considering it for topping.
Tbh, if it was me, id be looking at something new in a quality brand, drop the 4k as a deposit and put the rest out on finance over a few years, its good for the tax bill and at least you'd know what you have, take care of it and it would see you out.
That mightnt be what you want to hear but it might be the wisest move.
The day you buy is the day you sell imo.