This may be a controversial approach, but I've noticed when I'm cleaning machines that if I get Windex in the cracks around the button/trackpad, the cursor can go haywire, etc. Similarly, When the cursor is going haywire, I've found that if I spray a small amount of Windex into the cracks, wipe it off, and wait for it to try, sometimes that helps. I assume it's cleaning the contact when this is done. If you try this, make sure to only do it when the machine is off, and don't power it on again until the next morning to avoid the possibility of water damage.
I looked up the part and I didn't see it on iFixit...if it is out there and I just didn't see it, I'm sure someone will make note of that. I did a search for "A1095 topcase" on eBay and it did come up with a match.
Thanks!