Perhaps a step by step guide on how to post images inc ebay images might be helpful?

Nutman. I just looked on the yambits site. The Aussie piston you speak of says 1982 onwards in the blurb, despite it being included in the 74 to 77 bikes.

Yes, I know that is confusing. Wouldn't be the first time they have a mix up with dates and model id.

And if I understand it correct. What you do is link pictures available on the internet, but I want to upload my own pictures to this site. That is not working at the moment.

I seriously doubt Australia had different pistons from the rest of the world in 1976?

Yes, Tinkicker is correct that the original had a Dykes L-shaped top ring. Yamaha used those for a few years in the mid-70's.

What I'd be concerned about is that pistons need to be fitted to the bore... you might get lucky and another brand or type has the correct clearance but it could end up too loose or too tight. I've run into that several times. There are even slight variations in size from one piston to the other in the same brand and size. Which is why you need to have the piston in hand when going oversize so that the machinist can precision fit the bore to the new piston.

Have you had the bore checked? Often throwing in a new piston in a used bore can be false economy. Might be best to bore oversize? Make sure you find a quality machinist that knows these engines and does good work.

Anyway, I'd contact Enduronut here in the US as he's likely to have a brand new Yamaha piston and rings for a good price. If you have a machinist take measurements of your bore and piston, he might even be able to measure the ones he has for the best fit in your used bore.

If you decide to go a different route, the 175's tend to be very easy to find pistons for. You do need to check ring end gap location. Other than that, a piston from a 1972 CT2 through 1981 DT175 should work if piston and rings are bought as a matched set. Later models, which we didn't get in the US, may have a different piston pin height so keep an eye out for that.

Loading your own pic.
People seem to use Imgur then link them to here. I use google photos but not quite mastered linking photos live through to here.
Can put just the link to each pic indvidually on here which works, plus i guess it saves space on here maybe.
Someone will have a better plan. imgur.com/