What other pistons will work in my DT175B other than the 443 stocks ones?

Welcome from NZ. Someone will be along soon. Cheers & enjoy your time here.

Greetings from Tennessee 

eBay item number:383155563598
On ebay but price is expensive if still available. Say TY175 also so might help your search. I cant link ebay for some reason but hope someone can bring it up live.
www.ebay.com/sch/ebayadvsearch?_sofindtype=4
383155563598
Put just the number only above in the search link seems to work for me on here. Or maybe just do what i did first to get the full ebay page & i just put Yamaha 443 piston on my computer search bar & first thing that came up. Likely more better priced options out there.

eBay item number:234681821295
www.ebay.com/sch/ebayadvsearch?_sofindtype=4
234681821295 just put number only no words & it worked. Then hit the pic & the whole ebay page comes up so you can look down 'that' page at more possible options.

Are you using std bore or oversize? The DT175B I rebuilt last year is using an MX175A-B piston kit with great success (I could not find a single difference in the stock 443 DT piston and the 455 MX....ring pin pistion was exactly same too) and there seems to be a few around.
There are multitudes of 2N5 pistons listed on Ebay, some even mention fitting the earlier 74-76 DT and MX engines, but I haven't tried those yet so just be aware they may not be compatible.
Good luck!
-- Ray

EDIT.... the end of this post mentions you CAN use the newer 2N6 and 2A7 pistons in the older 74-76 DT's...ok then!
www.yamaha-enduros.com/index.php/forums/...4-75-dt-175?start=10