Platter wobble

Your only hope, if you want to fix this problem without spending money, is to try the method suggested by GK. Otherwise, you have a platter that is not flat. A flat platter is a core requirement in vinyl reproduction. If one of your rigid mats lies flat such that it is plane parallel to the arc inscribed by a tonearm, then you might get away with using a rigid mat. Otherwise, I would dump the thing.

Always wondered how anyone sells a complete turntable so cheap. It has to come in something that will at least survive transportation, and so at a certain point the box it comes in becomes one of the more costly "components". 

When it gets to the point where the parts are so cheap and flimsy one of the key components whose whole job is to just lay flat, and it doesn't even do that, well then Houston, we have a problem.

But you're determined to fix it for free, or at least cheap. If you can't bend it flat then here's what you do: Make yourself a new one out of MDF. Even if you have to do this entirely by hand my bet is it will be a big improvement over what you have now.

The way I figure it since many LPs are not flat it will all average out. 

Or if MDF isn't good enough you could upgrade to IKEA bamboo
https://www.youtube.com/watch?v=1sp37DxnKDY
Note this whole turntable cost less than the Technics. 

They've dropped the price by two bucks to $28 with free shipping!